Replacing is not such a bad idea because of age and serviceability. The dissicant cartridges on newer dryers are in the $40 range. If you replace I would suggest a move to a location that is more accessible. Mine is inside the left rear tire at the top of the chassis, it takes a pit to do it safely.
Monaco will charge a premium as you found. A change will likely require some different plumbing but the access improvement is worth it. While you are thinking of this replace ar least the wet tank drain point with a lanyard style instead of the kind you have to crawl under the frame to use.
