There's always different ways to look at a bike. First of all no matter how good of a deal you get some one else got (and will be happy to tell you) that they got a better deal. That's just the way it is. Remember the bike that you can buy
now has advantages over the "better deal" that's off in the future.
Lots of people started buying Treks after Armstrong started having success so there's lots of them out there. Some got alot of miles, some spent most of their lives in a garage. Where does the one you're looking at fall into this range? Check it out.
If you get a clean quality bike (and the Trek certainly qualifies as a quality bike) for $350 you got a deal that's pretty hard to beat. Bring cash and offer 275$, then 300$. The worst that happens is you pay the 350$ or decide to walk away.
But, you'll get told that you could have done better.