It might be $1,000 - $1,500 too high, but having been stored inside is definitely worth that much extra if it has ALWAYS been inside. Find that out and the history of ownership and then negotiate. In general the prices for used (and new!) RV's seems to be going up rapidly right now and there is a lot of demand. I just sold my TT on craigslist in 4-days and had multiple people wanting it. Because of that it's really hard to determine a fair used price. The ad you are looking at just went up a few days ago, so they probably won't be willing to negotiate much until it's been up for a few weeks. At $4,900 they are probably looking for $4,500.
Jefe will probably chime in on durability. He has a similar model 165 and takes it off-road all the time. Common issues for any old TC would be leaks with wood rot. Open things up and look for any evidence of water intrusion and problems underneath in the back.