Steve
My 98 Contessa was new to me in March 2011. I have owned boats for 40 years, with diesel engines, inverters, dc fridges, etc, so I thought my learning curve would be short. How wrong could I have been. I am still learning things about this coach that boating knowledge did not help me with. Read your manuals, but when things don't work the way you think they should, back away and think about it for a while. It is probably working the way it was designed to work, just in a way that is not intuitive to you.
Gary: no air leveling in the Contessa unless I got ripped off.
Steve: Things I have done to rehab/improve my Contessa
Better headlights, as the OEM were dim. I just bought better sealed beam units. There is a thread in the archives about putting in a relay to get more voltage to the headlight circuit. I didn't have to do that.
Better horns, as the OEM were wimpy. I bought Hadley truck horns at a truck supplier, Cheap like Borscht, but way better. I note that newer Beavers come with Hadley horns. No Beaver logo, so I put a Canadian Flag on the front of each horn.
Laminate floor where there used to be carpet. No more unsightly dirty carpet in the front cabin.
Snaky seals on all double pane windows replaced. Not just a Contessa problem, but Se-Gi window problem.
Front curtain and all OEM blinds replaced with MCD. Big improvement. See thread in the archives on this for pictures.
TV changed out for HD Flat Screen.
Full interior re-paint. Easy, and gets away from the dated wallpaper.
Window leaks addressed - This is the place that I think the manufacturer really fell down. The only thing keeping out the water is a 1/16" x 1/2" butyl strip sealing each window to the fibreglass skin of the coach. Once that fails, which it will, nothing keeps the water out of the plywood that forms the opening. The plywood is a big sponge, so the inevitable result is very messy. I doubt any motorhomes built in this era with the same windows are any better, so be aware and pay close attention to the state of the walls around the windows, as delaminations will show up. If you keep a bead of Lexel sealant around the outside lip of all of the windows, you may hold off serious leaks, but this does require vigilance. I live in the rainforest, so may be far more sensitive to this issue than most.
As for Diesel maintenance, so long as it has been done when you take delivery, these big diesels are easier to maintain and last a lot longer than the big gas engines you are used to, so you shouldn't have any trouble. Just keep your oil changed regularly, keep an eye on the clear bottom of the fuel filter, the air cleaner indicator, changing as indicated.
Enjoy your Contessa. Beavers generally have a great reputation for a good quality build. That doesn't mean things won't go wrong, they will, just not as often as with lesser brands.