Be aware you will be really disassembling the Mac Mini to get to the Ram slots. After you remove the black plastic cover and get to the Torx security screws be careful not to mix them as there are different sizes for the screws.
Finally when you go to insert the Ram take care to ensure the Ram is not inserted at an angle and is seated completely in the Ram slot. My roommate had to reopen his because one of the Ram cards wasn't fully seated in it's slot.