One thing to keep in mind is, the bigger the tire, the easier they are to change. This is true of tractor tires too.
It is hard to describe here, but I break my tires down with a jack. A floor jack works best, but other jacks do work. You just need to chain the jack down to the rim, then make your bead breakers with 2x4's.
As you jack up against the chain, it puts down pressure on the tire bead on four places via the 2x4's and blocks. That puts a lot of pressure on four points, then hit the bead with a sledge hammer. Within a whack or two, it will pop right off the rim because it has tremendous pressure all the way around the rim. It just needs a jolt to get it to go. (search Youtube for tractor tire changing and you will see what I mean).
Rims too can be repaired if they rot out by welding. A dealer quoted me $2000 for 2 rear rims and tires. I repaired the rims for $20 and got new rubber for $850 from an advertiser on this site with tubes. That is 60% less and the same result.
Most things you can fix yourself with a little thought. As an example my tractor seat was ripped, and cost was $60 for a replacement. A $3 can of spray foam, some self tapping screws and spray-rubber fixed it for $8. The way I look at it is: you can use your brain, or your wallet.