Surely it cannot be that hard, it's almost the last thing to go on. The hardest thing will probably be to get the roll hoops out where the tubes have been deformed by the securing bolts and a few years of muck and water ingress.
This sounds about right! You can put some effort in to the roll bars to get them back fully round while they are on the bench but you'll just have to squeeze them a bit out of round to get them to fit the out of round chassis tubes. Once cleaned up and squeezed to match the chassis, the roll hoops can be a bit of a loose fit; some paint can help them fit snugly. There's a fair chance that the rubber boots that fit round the hoops will be in poor condition by the time you get them out, it's worth having a new set to hand ready for reassembly and you might want to buff the edges of the holes in the body to get more even clearance round the roll hoops so that the boots can sit neatly.
None of it is terribly difficult but as ever when doing such things there is always yet another small detail that needs sorting out as you go.
Two people can lift the body off and back on reasonably easily but you really want a third to be running round checking and guiding things, sorting out minor snags etc. A fourth pair of hands might be useful at these points but any more might be just a way to start arguments.
A reasonably chunky pop riveter is a good idea, the usual small lever operated guns are hard going with stainless rivets. It's a good idea to use the correct size fibre washers between the rivets and the paint to give some protection, you might want to put some Dinitrol or similar on the rivets to give at least some psychological galvanic corrosion protection. Having some rivets available that are one size larger diameter available with matching drill bits is a good idea as some of the holes in the body and/or the chassis may have stretched slightly if there's been any slack in the original rivets. The design of the body to chassis tube connection is "obviously" with the rivets along the centreline of the tubes to give a proper, strong, equal pull up of the rivets...except it's not...the rivets are below the centreline, pull up unevenly within the tubes, so the "feel" of the rivet as it pulls up is a bit vague and odd. Luckily there aren't actually that many of them.
With the body off, it's a good opportunity to clean up all the unpainted bits of chassis and the bits where the paint has been worn so as to get it primed and painted something like how it should have left the factory. You don't want it in factory fresh condition, you want it much better than that and it's not difficult! Also a good time while you've got your can of Dinitrol or other cavity wax of choice to get lots of it in every chassis tube unless you can guarantee it will never see any rain, never mind salty roads.
If this is too deep into the "teaching granny to suck eggs" category, then apologies from me! It's a fair amount of work but no particular bit is too difficult or mysterious, but you'll be glad it's over once all back together.
