I''ve found that a mobile Rv repairman will know more about an RVP basement unit than a dealer. Use these to locate a nearby mobile RV repairman:
https://nrvta.com/
https://rvtaa.org/locate/
You can also run an internet search by zip code, either way_ ask questions about qualifications and experience when you initially call one.
The RVP 6535 unit if the most popular of the 5 different models. Here is
the service manual
The unit weights ~200# so pulling it out of the RV is much easier for 2 men.
This thread tells and shows how to pull the unit out, service and reinstall.
https://www.winnieowners.com/forums/...ure-42567.html
When I pulled mine and serviced it I rented a hydraulic table to silde the unit out on, while leaving it connected to 120VAC.
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2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA.
"We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution." Abraham Lincoln