First, why are you doing this? Do you know about Apple's logic board replacement program? It replaces the board for FREE if you have the video errors described in this document:
Now, if this has nothing to do with your issue, I would say just make sure you have the full take apart manual from powerbookmedic.com and read it over a couple of times before going for it. Have a couple little baggies for sets of screws (all taken apart you'll have a ton of little screws...) and some paper to diagram stuff out. Allow a couple of hours for the process. Don't rush it.
It's not that hard but it just will take your full attention!