adding a generator

See if Fleetwood can give info about generator wiring installation and fuel source in particular. Sounds like the setup without generator was for a rental unit.

You need 120VAC Wiring for the Output of the Genset and it sounds like you have that. Seems you have wiring for the Indoor Control Panel. VERY nice to have, but you can start and stop an RV genset from the geset itself. You have to have Battery Cables/Connections to crank it. And of course FUEL. I added a genset to our first C, a 1984 Holiday Rambler. It had everyting BUT the FUEL. Way back then I was able to reach not just the factory but somebody who'd worked on '84 coaches and hadn't retired yet. He told me "We didn't add a Fuel Line in Generator Prep." In my case, I was able to tap into a fuel line going to the engine. I could only do that because it was a carbureted engine with a low-pressure fuel system and a fuel pump that allowed fuel to be drawn through the pump when it wasn't running. EFI/MPI or other fuel pumps might not allow that.
Better find out if you have a fuel source.
What Make/Model/Year is your Chassis?
I got the genset (ONAN BFA 4KW) cheap used. Without a lot of luck, I'd consider a portable like a 3KW Honda Inverter type. I'd do pretty much what an onboard would do at much less cost and more quietly.

I believe an Onan 4000 KY will fit in that unit.

http://www.cumminsonan.com/www/pdf/manuals/981-0627.pdf