Yeah, breaking free the axle nut with everything still on the car will likely be easier than on the ground but not much, the same bolts & bar counter hold method will be needed. I can usually break the axle nuts free with a 1/2" gun without even bending the collar out, but I suppose that depends on the gun and the operating pressure. Try it with the gun first and if that doesn't work you've just got to go old school on it. Now's a good time to make use of the shopping cart you've been saving, cut the basket of and you've got a low to the ground cart! The carts they use under bread racks are perfect and you can get a cheapy moving dolly at home depot and harbor freight also.

The first thing I do is to remove the differential vent and screw a bolt into its place for the time being, that way you can flip the whole subframe over and not have differential fluid leaking out. Then get the lower control arms off that will give you easy access to the six bolts at the axle flange, get them out and pull the axles out of the way, mark what side they came from and you can swap them side to side if you want to. Then I'd do the differential get that out of the way. Then you can more easily flip the sub frame back over and get at everything holding the wheel carrier to the links.