Easy as pie
5 - 10 minutos
My dad had an old Macbook Pro that was lagging along on 2 GB of RAM. I typically turn to ifixit simply to shop - which I promptly did and ordered 4 GB of RAM.
This is one of the easiest repairs that I know (other than "turn your computer off and then on")... I would recommend this for any experience level. I helps introduce maintenance concepts.
Who can improve on perfection? A great guide.