We bought our '95 Cutter LE eight years ago. It needed a few things and we did some upgrades. We have been all over the US and have had very little trouble.
We can probably help you figure out some of this stuff.
We had our converter replaced when we bought our Cutter. The old one was mounted on the firewall in the driver's foot well. The technician installed the new one on the outside wall in the foot well and left the old one where it was. I later removed the old one to reduce usless weight.
Battery switch by the door
I don't think that switch is involved with charging. It just turns off 12 house power while the motor home is not in use.
I'll try attaching a wiring diagram for you.
Our cutter does not have a "transfer switch". The shore power cable is plugged into the outlet in the locker and when we run the generator the rig is powered just like we are plugged in to shore power. I'll try attaching a picture.
We got a Owners Handbook - Service Manual when we bought the Cutter. I don't know where you would get one if Airstream doesn't have it.
Hope this helps. Contact me if you need more help.