If you have to ask this question, then I'm assuming you don't have a lot of experience working on cars? If my assumption is correct, this is not a problem, it's great you want to perform this job. Just do yourself a favor, get a good repair manual and read up on this job. What seems like a fairly straight forward job can turn into a big mess if you're not prepared, so get a manual, read through the instructions, get any tools you need and get good quality parts. Leave yourself enough time to perform the job, and time to get more parts if you need them.
Try http://bit.ly/alldata_repair_manuals or http://bit.ly/mitchell_repair_manuals_online and get an online repair manual subscription. These are inexpensive and good quality.