engine numbers would be helpful buttttt.... the perimeter of the recoil assy should be 3-5 small screws. remove them and it should come off, the is as long as you have a eagerbeaver engine ( tecumseh ohv )
There is a thru bolt, and inside and outside bushing, and center sleeve. Remove those to remove the wheel. Obviously support the frame on a jack. Most tires can be removed using a slight soapy solution and 2 smooth screwdrivers. Replacement, use a soapy solution around the bead, and using only hand pressure put the tire back on. Use a cinch strap around the center of the tire to help keep the tire beads against the rim and air it back up.
As long as teh bead selas and the tire holds air, i'd leave it. Othewise, go to northern tool and equipment or fleetfarm and find a replacment rim. there all pretty standard widths and bolt patterns. Should be too expensive either.