Im probably a little overcautious, but I'm not in the market of a big investment getting damaged or dropped. You can see a few pictures in this thread of our rig off the ground with no tires for a wet bolt upgrade and cross member installation.
To get it up, I staged multiple sets of cribbing. Put 2 - 12 ton bottle jacks on the frame. Jacked one side up, cribbed, the other side up, cribbed etc until I got it high enough. Went up about an inch at a time. Once up, just used some floor jacks to raise / lower the axles into position. Did everything in sets (both rear bolts on rear axle, front bolts of rear axle, etc).
Being yours is a fifth wheel, do not rely on your landing gear to hold the front. Either block the frame / jack stand by them, or leave it hooked to the truck. The landing gear can and will fail sometimes, unless of course you're dealing with hydraulic legs.
Not the same project, but same concept. Might give you a few ideas. At least check the nylon bushing and bolt wear while you're doing all this. They don't last long.