1. Mileage. We replaced a 1998 Monaco with mechanical 8.3L with our present 2004 Winnebago with 8.3L electronic ISC. Towing the same car, same route, etc. we now get 7-7.5 instead of 8.5-9. Your numbers do sound a little bit low, but much depends on wind, towing, etc. Just offering numbers for comparison.
2. Air pressure. Sounds like you have a leak somewhere (to me, at least). Again the old Monaco would take something like 5 minutes to go from fully flat to full pressure and all bags inflated. The 'new' Winnie takes maybe 3 minutes (much faster). I'd say there is a slow leak somewhere in the air pressure system - based on ownership of far-too-many DPs historically.
3. Winnebago posts the tv wiring for their rigs on their website.
http://www.winnebagoind.com - look under the Resources tab at the top, then Wiring Diagrams - Motorized. Select the year, then coach, and the schematics are there. You will know for sure what was originally installed - but (again my experience), there is no telling who did what after that. I cannot fathom why, but RV owners seem to love removing disconnecting wiring (including under the dash) and leaving things disconnected/unlabeled - leave those who come behind scratching their heads if the system ever needs attention.
4. To find photos, one good place that has worked for me is Youtube. Do a search on the make, model, and year, and many times you can find someone showing a demo of your exact model.
Best of luck!