I would recommend having someone do it for you, I have a friend who has replaced every part of every kind of ipod, the first 15/20 that he worked on got destroyed until he got the hang of how to get into it and work with the parts inside
for parts and labor you would look to spend like... 45 bucks, give or take depending on time frame, and model of the ipod
if you are going to do it yourself go very slowly and be cautious, there are a lot of things that you can mess up VERY easily with the slightest of wrong moves