Boy have you asked a bunch!
We did a frame off of our 1963
Bambi. Our floor was totally rotted out except for about 2 square feet in the middle... Hubby took out all
interior furnishings. He had to remove the bottom portions of the inside shell to get the shell off due to blind rivits (can't see um...) that are in the frame members that go between the two skins that are part of the first stage of shell to floor construction. The two end caps and some roof panels are attached without side panels first. This probably sounds garbled, check out the thread below for pics and explanations, and also look at what others have done! Then he lifted the shell off. You will learn to love rivits!
I would definitely take the air conditioner off the roof. I think they barely support the weight anyway... the windows can stay intact. No need to open them...
Once you get the shell off you can then decide what you will need to do. This is the time to rewire and upgrade electricity, plumbing, etc.!
Big job, but worth it!
Here is my hubby's thread on the subject:
It is a loooooooooong thread, but has lots of pics.
Mrs. NorCal Bambi (traveling in S Tardis)