A couple years ago I bought the 2005 Original Discovery Channel Trek Team Bike (1 of 100 made apparently) on the recommendation of a friend who's brother rides professionally.
I've had it tuned a couple of times, but as a noob I have little knowledge in bike maintenance save for chaining tires, lubing chain, etc.
I've ridden the bike about 750 miles in the two years I've had it and recently took a bike maintenance class where we learned to measure the chain. The mechanic told me that mine needed replacing and that I should also replace the back cassette too.
The chain has never slipped on me.
Do I absolutely need to replace the cassette as well? How can I determine if I need to replace the cassette as well? How much is it going to run me? I would like to keep decent part on it, but don't want to spend a fortune (the mechanic mentioned that if I put anything better than "105s" on it I would probably be wasting my money)?
Matt in NYC