R1 / ag / agriculture tires = pizza tires per say, they sink and find the bottom of mud and keep you going
R4 = R1 but wider tires = balloon tires. they set on top of the mud and spin = stuck.
turf tires / lawn tires = generally approx same width as R4 tires and not as aggressive of a tire.
R4 tires and turf tires = good chance you can use same rim and switch between them.
R1 tires on other hand you need new rims if you want R4 or turf tires
if you tractor is a 4x4 / MFWD style of tractor you need to keep tire diameter ratio the same for front and back. MEANING, if you replace the fronts, you also should replace the back tires as well. or when you go into 4x4 / MFWD you could damage the drive train. due to either fronts pulling more than rear or vice vs.
pay more attention the the PLY rating, higher the ply the more rubber and/or thickness of the rubber on the tires. = in my own words. longer life of tire.
google AG tires or R1 tires or tractor tires and find the manufactures online. and do dealer lookup do this for a 2 to 4 tire manfactures dealing with tractor tires.
call each place even if they are a couple hours away and get a quote.
some charge by the hour, some by a flat fee, other charge per mile plus fees, each one is different. just call them up and get a quote most likely same dealers offer other brand of tires "name brands to off brand tires" the off brand tires can be 2x or more cheaper than name brand tires.
they will come out with new tires, and put them on the tractor right then and there. think tow truck for cars/trucks. but for tractors and swapping out tires. they generally also carry some fluid to fill the rear tires.
since this is your only tractor. i doubt you have a cherry picker or access to another tractor or something. to deal with the larger rear tires more so when filled with a fluid. you can get a tire filler valve i want to say gremplers name brand. and if you have say a 12v sprayer 20 plus gallons or so. with a handfull of other misc parts/fittings from a local hardware store turn your sprayer into a rig to empty fluid out of the rear tires and then once new tires on, refill the tires. ((there are other ways to empty tires and fill them up))
you still will most likely need some sort of cherry picker / lift / crane to physically man handle the larger rear tires. even when not filled with a liquid. *been there done that* and only way done was having the cherry picker. couple hundred pounds just a bit to much to manual handle trying to get tires back onto the tractor.
if you attempt to take old tire off the rim. yourself, along with possibly putting new tire on the rim. it is going to be additional cost for tire irons, to bead braker, to longer prybars. this is more muscle and making sure you have the correct tools. if you go this route get a tube, so you are not trying to dangerously set the bead of tire onto the rim. instead just inflate the tube and let it push the bead of tire onto the rim.
if you pay tire company to come out and do it, they have the tire irons, jacks, and good chance they will state to leave tires on the tractor, so they have something to pry against when removing old tires / putting on new tires.
some folks want the old tires, other folks want them gone for good.
pull your make/model numbers off your tires and have them ready when you call around for quotes, along with make/model of tractor along with if 4x4 / MFWD or not.
if no make and model of tires, make sure you measure diameter and thickness of rims. so they can figure something out.