I had slide covers installed on my 2015 MV with no problem. I know other folks have had them installed also. I suspect the 2016 layout and window placement isn't any different than the 2015. I would go to another RV dealer/repair shop and talk to them. Camping World isn't exactly known for their great service department.
2015 Greyhawk 29MV
Honda CRV toad with Blue Ox baseplate
Ready Brute Elite towbar with braking system
TST 507 Flowthru TPMS