The lug bolts are pressed into the axle flange. And yes you can get them at your local FLAPS. And, yes you can press them in or have a shop press them in for you. If you pull the axle then you have a good time to look at Drums, Brake shoes, Seals, Bearings, and Ring, pinion, and spider gears. Most common reason those lugs fail? Improper torque. Too little and too much. You might not be the person that over-torqued them but you will be the one to fix them.
I would pull both axles just to save doing it again later. I think they are 7/16 NF but match them up any way. Get some new lug nuts at the same time.
