You have two really good points to work from, a loose, corroded or disconnected ground is one and the multi use switch is another, I would expand the switch to include the entire electrical part of the steering column.
I understand that you're not real good at electrical work and there is an art to trouble shooting electrical systems. There is something that both you and any tech you might get to work on it will need, the drawings or schematics for the systems. If you go to the Winnebago Industries website you can download the electrical schematics for your year Itasca. The schematics are nice to have and not all independent techs and not all RV repair shops have them. I would download them to a CD or DVD just to have available.
The schematics are to a certain extant, generic, but, they do have specific locations for some system components. The schematics cover the entire house and part of the chassis systems.
I would also download the parts manual for your specific rig from same part of Winnebago's website.
Good luck on finding your problem and by the way, there are gremlins. Ask a NASA engineer or project manager. Space probes sometimes just stop working and when they do, the B.O(bad order) system is disconnected from the probe and the power is totally isolated from the system, the system is allowed to rest for up to and maybe longer than six months and when brought back on line will begin working normally. GREMLINS!
Oh, and there was an American Motors vehicle called a Gremlin too.