All HP and Compaq computers have very nice service manuals provided by HP. You can go to the support page for your model and click on Manuals (in the left column) to find it. They describe all the serviceable components and how to remove and replace them.
You might check this page, for instance:
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&lang=en&cc=us&docIndexId=64179&taskId=130&prodTypeId=321957&prodSeriesId=3466274#2