There is no telling what could go wrong at that age. You said it has a rebuilt engine. That's good but it also depends on how it was done. I have seen rebuilt engines go in without replacing the coolant bypass hose or water pump etc. Next hing you know it's overheated on the side of the road with a cracked head because of a $2.00 hose. My main suggestion is have money available to cover yourself out on the road. You are getting by without paying a lot so make up for that by having an "insurance" fund for repairs. There are a ton of things to check and I wont go on about it.
As far as boondocking or dry camping you will probably want 2 deep cycle batteries. It then depends on how long you want to stay out. If you limit the water pump and ceiling vent fan use and go with led bulbs you should get a few days or more. You may want to get a digital volt meter to monitor your batteries so as not to discharge too deeply. If you then go to a campground for a day you can recharge, dump and refill. If you want to stay out longer, then you need a way to charge the batteries with solar or a genny.
At the minimum you can run a cheap generator ($200 to $300) but do it without ticking anyone around you off. If you go solar its going to be much more expensive and become a project in itself. You have to size it properly and consider future expansion of the system.
You can charge you cell phone, laptop and other small things directly off your 12 volt system with a cigarette lighter type plug. You can even get 12 volt tv's and other things.
I use a 300 watt pure sine inverter to run two 24 inch led tv's and a laptop. I have a 400 watt modified also that I'm not afraid of and it was only about $40.00 at wally world.
Your traditional RV heater will be an issue as they suck propane and battery juice, depending on the model. A lot of people end up with catalytic type heaters that do not use 12 volts and are more efficient.
So, welcome, you have come to a great site with people in here that have been doing this stuff for a long time.
There is a battery voltage vs state of charge chart in the first link.
http://www.marxrv.com/12volt/12volt.htmhttp://www.solar-electric.com/deep-cycle-battery-faq.html#Lifespan
