I've been hunting around for a beater/commuter bike. The only real options out there in my area seem to be older rigid mountain bikes, and there aren't many of those in my size out there. However, if it survives grad school, I'd like to keep riding it, if lifestyle allows. I came across a 1992 Giant Iguana and am talking to the seller about taking a look at it. In the meantime, I have a few questions for the mechanically-inclined.

It looks like the parts are all original. This thing has Sun Tour components and 21 speeds. (Kind of dates it, doesn't it?) Do I have anything in the way of options when it comes time to replace anything--chain and cassette especially? Or does it make more sense to turn it into a single-speed at that point, given that I'd have to replace EVERYTHING (cassette, possibly the wheel, chain, shifters)? I'm also sort of concerned about the shifters, because I know nothing about Sun Tour or anything about bikes that old. (Sounds funny to say that.)

I will be chatting with the mechanics at work too.