You're correct in assuming the front suspension would be changed. The whole CG of the bike changes, of course. Some people do run the original forks but I think they change the suspension (softer? not sure). Surly makes a fork they call 1x1 which is a suspension corrected rigid fork.

Prevailing wisdom for your questions:

Steel but one of the hardcore xtracyclists "TONE" used an AL bike w/xtra to messenger in NYC
26in
No, but can work
I don't know of any

I'm still lusting after a freeradical and I've joined the rootsradicals group on yahoo groups. Very helpful and friendly people there.