After electrical questions, plumbing questions are the second most asked question in the Usenet forums. Small plumbing repair and replacement projects can be completed successfully by most DIY people. A few more tools and skills are required than for some of the lesser projects.
If you are willing to get your hands dirty and twist your back into some unusual positions, it is possible to save a few hundred dollars replacing a faucet or other fixture.
Sometimes though you have to be willing to admit that the job is beyond your ability and call a plumber.