I did this exact same thing on a 2000 a few days ago. There is a I believe 8mm socket in the middle from the inside and also an allen head if i remember right. I used a flathead screw driver though cause it fit and it's what I had at the time. Other than that feed the wires through clip it back on bada-bing-bada-boom. My thing is, though, the mirror is not flush with the door... I took it off and tried again 3 times and it's still not completely flush..
Please post on here if you have the same issue!!