I did it in a morning. Didn't take as long as I though, as most of it is pretty easy, just the wires bit.
Getting the base off the seat is easy, only a couple of metal tabs and a metal coathanger essentially.
For the wire hooks, I used long nose pliers and strong cable. For the front to back wire hooks I threaded the cable through the hook and pulled, worked really well.
It was the two side-to-side hooks that were the worst. My advice is get the wire roughly in place in the groove of the foam, then try man-beast it into place.
I got a good idea how to do it from this thread, and by doing the old passenger seat first.
http://www.golfgtiforum.co.uk/index.php?topic=65964.0