100,000+ miles over 5+ years in our Palazzo, and no 'blowout' concerns at all ...
with your only 39k miles, radiator and trans fluid are a LONG way from being any concern, maybe the trans fluid at 50,000, but the radiator fluid is about 100k...
use it, enjoy, and don't worry - those fluids are perfectly designed for MANY, MANY miles on these diesel heavy duty chassis'... even the OIL only needs to be changed every 15,000 or more miles.
Your Freightliner CUMMINS and ALLISON owner manuals will describe oil and fluid and filter change periods and timeframes. Most any large truck center or shop can handle them easily, or a Freightliner or Cummins or Allison specific shop. RV dealers, though, are probably NOT the best places to use, at least for the 'chassis' needs. Freightliner's OASIS RV shop, in Gaffney, SC where these chassis' are built, may be a great option - on-site free full electric and water hookups for your stay, and they usually can do everything in a single day.
Another option is SPEEDCO truck service centers - easy in and out drive-thru centers - no appointment, just arrive and wait in line. They will typically do oils and radiator fluids, even for your generator, but not transmission fluids.
two Campers, two Electric cars
former diesel pusher traveler