It's an easy job if everything's in good shape.
But your rear bushings have already fallen out. Are the bolts still there, or did they rust through and break in the middle? Your big problem is going to be extracting what's left of the bolts from the nuts in the body and making sure the threads are in good shape. If they aren't, you're looking at getting the body far enough off the frame to cut the old nuts out the body, weld new ones in, and then moving forward with the rest of the bushings.
After that, you just park the car on a completely level surface, loosen (but don't remove) one side's bolts, remove the other side's bolts, jack the body up off the frame just enough to remove/replace everything, set the body back down, run the new bolts in loosely, jack up the other side and replace everything on that side, set it back down, try to re-center the body on the frame, then tighten it all up.
If you're comfortable with that, go for it. If all goes well, you could do it by yourself with two jacks and six jackstands in a day. If all goes poorly, you'll be cussing and throwing stuff everywhere.