Mountain Biking - What to look out for in buying older mountain bike

I know absolutely nothing about mountain bikes. I'm a roadie/fixed gear person. However, I have a chance to pick up a 2000 Gary Fisher Big Sur this evening for a good price. What do I need to look out for? Would it be safe to assume the frame would still be OK after 7 years? Do the aluminum frames last? I haven't a clue how hard it's been ridden. I suspect the person that owned it rode it pretty good. It looks to be in very good shape though. Thanks in advance for input. As I said...I know nothing about this type of bike.

I would examine the aluminum carefully for any possible cracks. How much do they want for it? What kind of components are on it? There are a lot of factors to consider. Pics? -GT2005

Lots of extremely important things to know. I gotta go somewhere though, I'll tell ya tomorrow.

Look at any thing common sense says about buying a metal object possibly subjected to physical abuse. Cracks in metal Loose parts, not always a big issue but inspect areas with this problem should it be present. If your not planning on an immediate rebuild look at the brakes and wheels. Wheels should be free from stress cracks obviously. If you are buying it for the frame, look at the frame. Cool, huh? If the bike shifts poorly it may need new housing and cables, again no real issue but it allows you to bargain down some. If in doubt have it inspected by a bike shop.
Some allow aluminum frames are are done after five years of hard riding but I stretch that to "till the frame breaks on me" if the bike is a single owner and the owner is physically similar to me. That's me though. i have a 92 Gt Backwoods that still sees minor use. It's been beat to piss but I bought it new and know exactly what it's been through.

Certainly you should check the frame, rims, hubs, brakes, shifters etc. As someone who is familiar with bikes, but not familiar with mountain bikes, I would also focus on the fork. Is it original or updated with a better replacement? Has it been rebuilt? When? Is it the old elasotmer type? In my limited experience dealing with a few freinds new to mountain biking, they see a suspension fork and assume nothing can go wrong with it. But when you think about it, on the trail, what part takes a huge amount of abuse? Make sure it isn't leaking if it is an oil damping fork or an air spring fork. If it is original equipment, maybe it's time to replace it or at least service it if the owner has not kept it up. Factor that into the price.