Unless it is totally rusted, rotted, and ruined, that is a good price for any TD... have seen frames without wheels sitting in fields that go for that!
The frame, as mentioned is steel...the body has a wooden frame of ash, again as mentioned, which has its metal skin tacked to it...
Quarter panels usually rust (mine have), but all the tub panels are pretty much flat metal... not too hard to repair or replace.
If the wood is rotted (you can see wood around the firewall where the body panels meet it...usually painted, but wood just the same and the ends of this wood can be seen from under the car), it becomes a pretty major job to rebuild.
You can build a new TD with parts from Moss and a few others, however, they are offshore and can be tough to fit...not to mention not quite the quality of original...
Check eBay and you will find hundreds of hits for MGTD