My old Gabrial air shocks were leaking on my 1991 Jeep Cherokee XJ, so I ordered a set of Monroe Max from Amazon. https://amzn.to/2niPoCh
I began by spraying the top bolts with PB Blaster. https://amzn.to/2nj1taA There is access to the top of the bolts through some openings in the bodywork. My top bolts came out easily.
If yours break off, Rough Country makes a handy kit for an easy repair. https://amzn.to/2nwFz3B
The lower nuts are 18 mm and usually come off easily. I used a pry bar to remove the lower shock loop from the pin. If the lower shock mounts are broken, they can be repaired by cutting off the pin and drilling a hole in the mounting plate. Use a ½” bolt to replace the pin.
I coated the upper bolts with anti-seize and started one in a few threads. I then hung the shock on the bolts while I started the second one. Once the uppers were tight, I slipped the lower loop over the pin. IF the Jeep is suspended so that the axle is at full droop, then you will need to lift the axle some to get the loop over the pin. I used a soft-faced hammer to tap the loop onto the pin. I then tightened the 18mm nut.
Next, I installed the airlines being careful to route them as far away from the exhaust as possible. I ran the fill valve through a hole in the bottom flange of the bumper and secured it with the supplied nut. I then added enough air to inflate the bags and checked for leaks using soapy water on each of the tubing fittings.