I'm in the middle of swapping mine out. It's pretty straight forward for the most part, but I will agree about the instructions. I was reading them before the tear down, and was thinking there was a lot to it, but it's actually the opposite. Before you know it you will be 3/4 the way through them. They are very detailed, which is never a bad thing and makes it seem like there is a lot to do.
Only problem I'm having is getting the little lock washer on the fuel sock. I messed with it for about an hour last night before I finally gave up and came in for the night. I heard 99's are different though and don't have that little lock washer for the sock. I haven't got around to installing the harness yet. Will try and tackle that today if I can get that damn sock on.
All in all it's a pretty painless install. I would say it should only take a couple hours start to finish to get everything done ( I did the trap door). The thing that takes the longest is repining the connector, and even then it doesn't take that long.