7 - 10 Minuten
Only had 1 GB of RAM on an older MacMini, and needed to bump it to 2 GB.
The repair was smooth.
Take your time, and match pictures of the guides with what you are doing. Use a magnifying glass if you have one, to scope things out as you are taking things apart. Even take a few notes, I did, as you go along. Be sure to have all tools and parts at hand.