What problems are you having?? You may want to post to the Monaco owners forum, you will get more views.
The fuel gauge may OK, it may be the sender itself. Centroid provided the sending units on Monaco coaches. Here is a link CENTROID PRODUCTS - Electronic Fuel and Water Senders
Calibration and troubleshooting is down the page. It might help to start by removing and cleaning the wiring on top of the sender unit which is mounted on the top of the tank. There may also be a calibration screw, it is hard to see as they seal the screw, I finally found mine and did calibrate, it helped.
Engine oil pressure may be due to sensor. You can create an account on the Cummins Quickserve site, then put in your SN, and then see what sensors there are. https://quickserve.cummins.com/info/index.html
They are usually fairly easy to access and would something you could try.