The point isn't that it would or wouldn't void warranty. It's simply not something that Apple will do for you. Apple will fix a problem with the computer - for example, if the unit was clearly overheating outside of its normal specifications under normal usage, that's something they would address. But they have their own methods of correcting problems - it might be economical for them to just replace the computer, for example. They won't mod your computer for you, or take instruction how to do repairs.
If it's something that you want to go ahead and do anyway, whether by yourself or through a (non-AASP) technician, then yes, that would almost certainly void the warranty.
Matt