Check out General RV in Huntley.
https://www.generalrv.com/rv-dealer/huntley-illinois
I've been there to buy parts but never had any work done by them. They are right off I-90 in Huntley, and they are a large dealership.
The dealership where I bought our trailer is in Wisconsin near Milwaukee, about an hours drive from where I live. I had work done by them with no problems, but I'll only go to a dealership if it's something I can't handle on my own. They used to be Burlington RV and are now Lazydays RV, you can check them out as well.
https://www.lazydays.com/rv-service