I found a 2007 Trek 520 that someone is selling. The bike seems in good shape for it's age and is the right size for me. The owner wants $700 for it though. Is that too much, considering that the bike is 4 years old?

I plan to go on a loaded tour later this summer and I want a good, reliable touring bike. Is the Trek 520 a good touring bike? Or should I keep looking for something else?