So long as your AC is not the whisper quiet, there are two tabs that you push in under the AC unit(s). Pull down while pushing in not up on the tabs. The cover will come off. Be careful cleaning. I used Dawn soap while gently moving my hands over the foam filter. It is not hard to clean, but the foam is delicate. Dry it with a towel. I used dental floss to strap it to the access panel and put it back. The dental floss really helps keep it in position while reinstalling the cover. I would take a picture, but my fifth wheel in in storage at this time.
If it is a whisper quiet system, the return vent side has filters on each return vent as I have read here in the forum. Each vent would have to be opened up to get access to the foam filter. Then clean.
Other than that, there are no serviceable parts. If it breaks, it has to be replaced.