Hey there! I know a few of the bases have been covered, but I figured I'd go through and answer any of the ones I know. (By the way, my team, 1293, was a rookie team last year. We started from scratch as well.)
First, don't lose sleep over materials. Teams have made their robots out of everything from aluminum to plywood, all with high degrees of success. The two-speed transmissions and all are nice to have, but are by no means required to be competitive.
With 25-45 team members, you'll be fine. 1293 was about that size last year, and we had a pretty good rookie season. Programming in C isn't too terrible (shoot, I got the robot moving once). As for previous supplies, don't sweat it--it might help in building faster, but they've got the same limits as you (usually the kit plus $3000 in extra stuff, but that's subject to change).
While the 2004 game won't be what we see next year, I'd highly recommend checking out
www.soap108.com for some videos of matches. It should give you a good idea of the size, complexity, and variety of the robots.
And while I may be biased, I'll say this--you won't regret joining FIRST.