The repair is not too hard, if you are up to it, you have a loader to break the bead, I jacked my old 850 up, put jack stands under the back, solid and wide cribbing, then rolled the tire to the loader bucket and used that to break the bead, I do have a set of spoons from TSC, some rim glide lube, and went to GCR in Menands, NY for a quality or probably the best tube available off the shelf, like its all not from china anyway these days.
I repaired the rim by welding, but the tire MUST be completely off the rim, Pyrolisis can and will detonate if you weld on a rim with a tire mounted. Left the raised weld profile on the outside, ground smooth on the inside, I used zinc galv spray on the repair area. I think you do have to change valve cores periodically, I have in the past. That last repair had a valve leaking for years, it trashed the valve hole but nothing else, valve failed though, so I had to get a new tube, and of course it just blew out and made a mess, well killed some weeds LOL. Tire guy is usually out of my budget, but I did watch and learn the last time I hired one, so it was worth it, as I can do these myself, not as quick but I don't have to wait on someone and or pay a premium. I drilled a new hole, no flat spot though, I should have heated and made one, but the tires been over a lot of acres now, held up just fine, and was just some typical repair work to do it myself.
The only thing is the special valve adapter you will need and or either a pump or set it up to fill by gravity if you can, CACL flake is cheap by the bag. Also wash and flush things real good, my friend had some kind of small garden hose size pump, worked great but it failed soon after, not sure but CACL maybe had something to do with it, and it was flushed thoroughly, I always over do things like that, maybe coincidence, tire guy has the nice pump, so when time mix up batch in a barrel, and pay him to load it if possible.
We have a 3600 on the spreader at the horse farm, same deal as you and won't mention its rims, uuuugly, of course its not mine, but it has double rings chains on it, a must have, don't believe those are loaded tires on it, but those chains help. I got a new set for my 850 last year, well worth having, even with CACL loaded tires and a real heavy cast iron weight, will have to put them on tomorrow for the winter, at least its in a heated garage LOL !