Craig_AE86 and I did this one before, however we used an AE71 pedalbox into an auto KE70.
you will need to get a holesaw bit to drill a hole for the clutch master, and this is a bitch, because you either have to drill from inside the footwell or make a guess.
however there is no reason to take anything out apart from a few trim panels under the dash. from memory, you might have to drop down the steering column down, but this is no biggie at all, and I think it is just for access purposes.
the best piece of advice I can give you is to look at how it goes together in your AE86, and then just transfer it over. It should be a fairly straightforward procedure.