I work in a tire shop, I can tell you the hard part is getting the tires off the rims. They have rib made into the rim that keeps the beads from breaking down with such a low pressure. That makes them a biotch to break down. If the old tires are trash, The easiest way to break them down at home is to cut the old tires off. Some other options are, Take a jack with a flat base, and put the base on the tire and Jack it up against something solid or heavy. Using the jack to break the bead. You can use the claw end of a hammer on some tires, You strike the tire with the claw end, pushing down and sliding it between the tire and the rim right at the bead at the same time.
cutting them off, you cut the tire from the rim, just leaving the beads on the rim. Then from the inside take a chisel,grinder, dremel etc, and cut trough the bead, it will release from the rim, pop it off with a screw driver or by hand.
Getting the new ones on Just lube the beads with soap, The first side you should be able to slip it on the rim with just your hands if you can hold the rim still, it takes some force.. The other side I start by hand about 1/2 on, then work it on with a flat screw driver.
Beading them out. I don't care what they say about pressure, I have to inflate them to around 40-50 psi to get the beads seated. Then adjust to the proper pressure.
If the tires are narrower than the rims,then you will have a hell of a time beading them out.
we get $8 a tire to mount ATV tires. I make it look easy with the proper machine, I can tell you Its worth the $8 not to do it at home.
Later Glen