those are differently wired options - the Nav monitor is wired to the back of the car for the Nav functions and for the radio, which is in the trunk, and the high/low MID is not wired to the trunk, as the radio and all computer functions are at the front.

so, once you remove the Nav, you need to do a MID retrofit, which is essentially downgrading the car and not upgrading... you will need to either abandon the Nav loom and do a complete MID harness install, or spend a considerable time studying the WDS diagrams in order to rewire the exsisting Nav loom into the MID set up...

no easy way - unless somebody already had spent time and effort for this particular setup and has a ready-made solution...

I have a PDF detailing the upgrading - going from MID to factory Nav... but you don't want that...