I hadI one a long time ago. It was a carbine in 308. It would bring top dollar today. Like Jake said, it depends on configuration, chambering and condition. They are a popular rife here in PA with the 30-06 the most common as is the 308 and 243. Average price is now $400-$500 I believe. They are really pretty accurate but also a bit on the heavy side.
I'd bet that rust you're talking about can be removed with some oil on some 00 steel wool.