Check it out in person. $350 is a good price for the bike, if it's in decent condition. One thing to check is the sides of the head tube. If there are patches where the cables have worn away paint, then it's seen some miles. It's a problem I've noticed on Treks, and it's generally the first thing to show wear, so it serves a useful purpose of letting you know whether the bike has lived in a garage or not. So, if there are worn patches, more inspection is required, if there are not, I'd say it's a safe bet that it's in good shape.