I just left my local Ford dealer after they refused to service my F-53 ford mo ho on the grounds that it was too big. Now ths is not a old time Mom and Pop dealer, this is a dealer with multipal brand...
In your Ford F53 op manual and warrantee book you should have a number to call at ford spec for MOHO factory work. They will locate a Ford location in your area that will agree to do the work. Or course in west Texas it may be several hundred miles away. Something simple like an oil change you are probably on your own, but as others have suggested above make sure it is a copetant supplier with low personnel turnover.