I have one of these 720 bikes. I got it used recently, after a repairman tuned it up. At first i didnt like the grip shifters but now i like them better than another used bike I got, an old Univega hybrid that has trigger shifters.
On my Univega bike, which is a similar model that competed with the Trek, I just got a new chain, cassette, and used front derailler (because my old one got broken when my chain broke and the cassette was worn.) One option for you would be to stay with your old shifters and old deraillers but just get a new chain and new cassette (probably a 7 speed cassette like my 720 has.) A new chain and cassette are approx. $20-25 each so its not a lot of money and it will make the bike shift much better if your old ones are worn. I use a local mechanic who knows how to install/adjust things very well, so thats a big factor too. I think you should ask yourself whats wrong with the way it is stock. If it is just worn, then you can get a new cassette and chain. If it seems out of adjustment, then that's something a good mechanic can adjust. To answer your question about components- my understanding is that the hybrid bikes like the 720 use mountain bike components (ie shifters, deraillers, cassettes, brakes), there has been very little in the way of special hybrid components made by any manufacturer from what i have read.
Last edited by GaryinLA; 09-24-11 at 03:43 PM.