replacing fan, adding ram what else should I consider?

She's an oldie but a goodie, and her warranty is no longer active. My husband is in the IT field and we are computer literate -- make and tear apart PC's all the time. I'm looking for those with a lot of experience on macbook's to provide feedback, since I had the warranty until recently I never really messed with it. While I have it opened up - replacing the fan and adding ram and a few other things, (fan started messing up and it slowed down pretty bad on my last trip) is there any specific things I should look at and replace while 'under the hood'? I use it mostly for writing, research for work, and college classes, and some light photoshop work. Video's and music while traveling (which I do a lot of.) Is the heat sink that attaches to the processor worth looking at, anything else that is a known problem or known to wear out with this model? Thanks in advance