Hi Tom and welcome to Air Forums. I think you will find answers to your questions concerning your new 77 Sovereign
right here, but not likely from me!
I often leave my trailer hooked to shore power with the battery disconnected. Old style converters over charged batteries, the new ones are better. But you won't be boondocking soon, so no battery needed. But don't tow your trailer without a battery. It powers the emergency brakes.
I assume you will also have city water available, and a sewer connection. Dumping waste water tanks is a real pain. If your guests include teenagers, you can expect long showers using 30 gallons of water. Then the 1500
watt hairdryer starts up. You will use all of your 30 amps running the AC on a hot day. Make sure you have at least 30 amp service to your rig. You might like electric heat for cool nights. An on demand electric water heater might be nice. Oversized propane tanks with automatic switching would give you extra time before running to fill the tanks.
Old Airstreams leak. Many old Airstreams, like mine, have rotted plywood floors due to the leaks. You're going to have to check for rain water leaks and rotted floors. Learn how to reseal seams, windows and doors. Please don't use silicone calking. I wouldn't worry about axles, brakes, shocks and bearings if you are not going to tow your trailer. Your tires will dry rot in 5 years or so.
Do get a 115v circuit checker from your hardware store and check every outlet in your trailer to insure you are properly wired and grounded. Make sure your bathroom, kitchen, and outside outlets have ground fault protection. Upgrade your 115v electrical system if needed. You don't want your guests ending up with curly hair!
Our Airstream has been used as a spare bedroom before. It works great, and kinda fun for visiting family members. I remember my son asking why there was 5" of water in the shower pan! Water usage while camping is different (much less) than water usage at home.
Again welcome, and enjoy getting your Airsteam ready for your guests.