ifixit.com has good step-by-step instructions. I used them to upgrade RAM in my 2007-vintage Mini (not for the faint of heart), and to replace a hard drive in an old G3 iBook (not to be attempted by the sane). The older Minis are a pain, with putty knives to pry the case open and all that jazz; the recent ones, since mid-2010, it’s dead easy. There’s a panel on the bottom that screws off and the RAM is right there.