Welcome Debora, Like any old camper it is wood and for the most part after 43 years probably is in need of some frame repair somewhere, even if you can't see it. If it has high-jackers camper jacks on it you can still buy rebuild kits for them. No matter how bad they leak they are easily rebuilt and darn near indestructible. Electric I would assume old style Atwood's that are in the same league as the others. If your going from a motor home to a TC your in for a shock cause TC'rs are generally pretty small. You probably won't realize that until your first night under your overhead cab that's a couple of feet away from your nose. Anyway welcome to the forum!
As far as your manual the best place I can think of getting one or a copy of one is Lance campers directly, LOA forum or EBay. Of course that's assuming you can get one and they had one.
The fridge is a tuff one cause camper fridges are top dollar for the bottom of the line unit but a good GE dorm fridge would work perfect especially if your going to concentrate on 110 volts. I recommend the latter. That's of course if your not planning a cross country trip just local so it doesn't thaw out.
That's a good switch off from a holding tank to a Porta potty. I recommend as well.
The cable coming out that has been cut is likely your shore line which will be 110. It should be about an inch thick but if it's smaller it may be your truck to camper cable but you should no that coming from MH"s.
I guess everything else has been covered above so good luck.
I would look for any water damage before I put a dime into it.
Joe