I didn't have any records with the coach when we bought in 2008. I took it in for a full service but that didn't include transmission oil change. I called a local authorized service center and was quoted $650 OUCH. I did some research and decided to do a complete oil and filter change myself. It wasn't hard.
After 4 years I did a filter change, lost ~1 gal on oil.
At minimum I would take an oil sample and then do whatever is recommended. If no problems just change the filters.
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi