I believe that Freightliner is required to authorize shops to do their mileage based services so you don't have to go to a FL shop. I know I wouldn't because of their horrid pricing schedule for RVs. Far beyond reasonable.
So, what you could do is check RVServiceReviews
for your area shops, and or shops along your travel route, and check for shops that would be praised by your fellow RV'ers. It's a subtle process that requires that you read between the lines on the various reviews. And of course nothing beats visiting the shops and the workers. Naturally, call them and make sure they can do the authorized required services. Usually that's not a problem with a halfway decent shop.