If you want to do it yourself here is the best tip you’ll find. Jack:
One of the best locations to determine which Macs can be upgraded and which parts would be required is iFixIt. Nearly everything you need to know about iMac, MacBook Pro, MacBook Air, MacBooks, Mac mini, and even older iBook G4s and PowerBook Gfs are available with a click or two.
iFixIt is an incredible site.