Don’t do it yourself – unless you are confident.
Here are a few links to plumbing D.Y.I.’s gone bad. Enjoy!
http://www.elocalplumbers.com/blog/diy-shower-valve-replacement-wrong-526
http://www.picifix.com/diy/ag21409.html
http://www.youtube.com/watch?v=V7aVdZLkO2s
http://www.homeimprovementpages.com.au/article/diy_plumbing_in_the_bathroom
http://www.servicecentral.com.au/resources/articles/Plumbing-gone-wrong/278