Most private sales have before and after pictures of the paint tuneup. I see nothing bad about new paint / decals. As long as it did not double the machine price. Alot of hours doing a good job and its only cosmetics. One still gets to try out the functions.
Sorry I didn't get back to you earlier but if everything checked out good I would offer about $5000 to $5500 max. I have an 820 which is 1973 and is practically the same machine. I have a rops and canopy on mine and it has jut over 1500 hours on it.