I've never been into the Patio tractors, as to me they just aren't John Deere's without the Green and Yellow paint. Just my opinion, and no ridicule intended. However, I have noticed over the past couple of years, that certain tractor models and colors bring higher amounts at auction, than some of the others.
For the most part, the easiest or more common models to find are the 110's and 112's, and the more commonly found colors are the reds and blues. With this said, you have one of these models and colors. I'm finding for the most part, that the 140's and 120's are the more highly desired models when it comes to adding a Patio tractor to someone's collection, and since the red and blue color options are more plentiful to find, collectors will spend more money for the harder to find yellow and orange color options. So what does this mean for you?
You have an average or commonly found patio model, and it has the more commonly found red color option. I personally don't think that you will get anywhere near your time and effort money value back out of the tractor if you should decide to sell the tractor sometime down the road. Right now, I'd value your tractor as it sits, right around the $500-$600 range. Even if you'd restore the tractor to factory specs, and have the finish back to showroom quality, I can't see that you'd be able to get more than maybe $2,000 for it. Not due to you efforts or workmanship, but still due to this being a commonly found model and color. Now if the original color would have been the yellow or orange, you may be able to get a little more for it, however I'm thinking not more than maybe an additional $500-800.
Let's say the model would have been a 140, and the color would have been the yellow. You could very easily restore the tractor and most likely sell the tractor for between $2,500-$4,000. I know it's a hydraulic tractor compared to your gear drive, and I realize that I'm not comparing apples with apples, but I'm trying to prove a point that when guys say these patio tractors are selling for up to $6,000-7,000, you have to understand that not all patio tractors are desired the same way or of equal value. You mentioned that you will have the seat recovered. If it's not an authentic "John Deere" patio seat, you can't expect to get the prices that some of the other tractors that have the authentic seats are bringing. Just throwing that out there for you to consider.
If the tractor was mine, I would restore the tractor to my expectations, and forget all about selling the tractor to make money. You could have a very nice piece there, so do it over, enjoy your efforts, and pass it down through the family whenever the time comes. Good Luck to you Sir, and I wish you well.