Bathroom remodel © Digital Vision, Photolibrary

Do-it-yourselfers' tales of disaster aren't hard to find.

Chris Hubbard of Thousand Oaks, Calif., recalls when he and a friend decided to change the oil of his first car when he was 18.

"Well, we drained the oil just fine, but didn't know where to put the new oil. We thought it should go in where the dipstick goes," Hubbard wrote on my Facebook fan page. "Turns out we used the wrong dipstick and put the oil in the transmission fluid. I drove the car for 3 days with no oil and oil in the transmission fluid. Ended up costing several hundred dollars to fix and later got my engine rebuilt by my mom's boyfriend."

Lindsay Cowdin of Fort Worth, Texas, thought she and her husband could remove the old acoustic ceiling tiles in their family room, replace the old drywall, install new insulation and put in can lighting. They thought it would take them one or at most two weekends to get the job done.

"We quickly realized our miscalculation by how long it took to remove the ceiling tiles," she wrote. "Several weeks later we gave in and called a contractor. My husband is completely capable but had to bow to the clock. We just couldn't live with our family room in disarray for so long. The contractor knocked it out in two days like it was his job -- because it was!"

After 25 years of being a part-time mobile DJ, Steve Stewart of Saint Peters, Mo., opted to do one of his own events.

Liz Weston

Liz Weston

"I decided to do the set-up and tear down of my equipment FOR MY OWN WEDDING RECEPTION," Steward wrote. "Luckily I have a few DJ friends who were happy to take the mic and run the show so I could enjoy myself. Not a disaster but definitely not recommended DIY."

Sometimes, doing it yourself makes a lot of sense. You save money and get satisfaction from a job well done. So how do you know when DIY is a good option, and when you're about to get in over your head?

Whether it's a project involving your house, your car, a big event or your finances, you should think twice if:

Your attitude is, 'What could possibly go wrong?'

If you can't list several ways your project could go awry, then either you don't know enough about the task to attempt it or you're not thinking clearly about what's involved (sound familiar, Steve?). You may get some insights by talking to more-experienced DIYers or doing more research. If large sums of money or legal documents are involved, it usually pays to consult a professional.

You could kill yourself.

Courting death or serious injury in pursuit of thrift . . . yeah, not such a great idea. That's why projects such as tree trimming, asbestos and lead paint removal, and anything involving natural gas lines or 220-volt electric lines are best left to the pros. Most financial decisions aren't going to get you killed, unless you borrow money from a mobster you can't pay back. But you could effectively kill your financial stability by taking excessive risks, such as putting most of your money in a few stocks or falling for get-rich-quick schemes.

You could do a lot of damage that would be hard or expensive to fix.

I learned about this one the first time I turned on a floor sander and promptly gouged a big divot in a friend's hardwood floor. He "fixed" it by positioning a piece of furniture on top. Plumbing repairs are another DIY project that can go expensively bad, since even minor leaks can cause water damage and mold that cost thousands to fix. For similar reasons, you'll probably want to consult a fee-only planner a few years before you retire. Mistakes made in the early years of retirement -- such as withdrawing too much money, taking too much or too little risk, or taking Social Security too soon -- often can't be fixed and could cause you to run out of money before you run out of life.

The job requires skills you don't have and couldn't acquire easily.

It's not hard to learn how to patch a hole in a wall or change your car's oil (if you take the time to read the manual, right, Chris?). If, on the other hand, a job is typically done by a highly paid tradesperson, you might want to think twice before tackling it. Electricians, plumbers, mechanics, masons and even drywall hangers don't learn their trades overnight, and neither will you. By the same token, taxes and estate planning are two complicated areas of finance best left to those who make these fields their life's work. You can DIY if your situation is dead simple, but as soon as there's real money at stake, you should call in some help.

You need expensive tools you don't already have.

If you can't borrow or rent what you need, consider carefully whether you want to make a big investment versus hiring a pro to do it for you. Even if you can rent a tool, the project may take longer than you think, wiping out any savings from doing it yourself.

Somebody else could do it a lot faster and a lot better.

Painting is often offered up as the perfect DIY project, since most people can do a decent job as long as they do the prep work and have good tools. If you've ever hired a professional painter, though, you know the difference between a pretty good DIY job and what a pro can accomplish in a fraction of the time. The pro has already made all the mistakes you're going to make, learned from them and improved. The pro starts with all the supplies needed, so there's no running back and forth to the hardware store. The pro does all the cleanup, which, if you've dealt with the aftermath of a DIY, could be reason alone to hire one.

You really don't want to do it yourself.

Some people love spending hours fiddling with their investments, researching exactly the right backsplash material or tracking down parts for their vehicles. Others would rather eat glass. If you're approaching a DIY project with dread and apprehension, pull out now. Paying someone else to do the job will almost always be better than forcing yourself to do something you hate just to save a few bucks.

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Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.