As you have probably deduced or know, the gist is that you disconnect the shocks etc. and more or less attempt to lift the Jeep off of the axle so that you can (in my case) take the springs out, put the spacers in and put the springs back in.
This means you have to be able to lift the Jeep frame/body high enough to unload the spring(s) and take them out while making sure that you don't over stress (stretch) things like brake lines, locker wiring etc. The sliding "jacks" on our hoist were barely enough to do this even with all the rubber blocks in place (scary stuff I tell ya)!
I couldn't say how high I had to lift that sucker. Having seen what happens at the show 'n shines, almost makes me thing an RTI ramp would be ideal... put one side on the ramp so the other side unloads, drop the spring, put in the spacer, put the spring back in and repeat on the other side... then do the opposite end the same way.
Perhaps someone can shed some light on how high you have to go to get this to work?