not a door, per-se. But I installed a garage door opener... I got the costco 150$ one, it was daunting for the first few hours as I took all the guts out of the box.
it took me 2-3 days of just learning the pieces, their purpose, and what could possibly go wrong if I didn't take my time...
It turned out great. There's parts where a second set of hands is really needed. it was for a single small garage, and turned out pretty cool. only thing that sux is that when it rains, the door jams half ways.. i'm thinking its a crooked door to begin with, but that's about it.