Quote from Chuck:
Is it possible to upgrade a late 2008 15" MacBook Pro with newer logic board? Thanks.
No, the logic boards are made for the specific model and will not work (Fit) in other ones. However it is possible to replace the logic board with one for the same model but with a faster processor and more video memory depending on which configuration you currently have. Now finding that logic board is a different matter.
Quote from willpower101:
you forgot to mention intel based processors
The processor is not upgradeable, as processors and graphics (whether discreet or integrated) in most if not all notebooks are soldered onto the logic board... So if you want to upgrade your processor from Power PC to Intel (Or just get a faster one) you must purchase a new notebook.