2003 Newmar Dutch Star Spartan Chassis - Replace dash radio

[2B1Ask1]

We recently purchased a one-owner 2003 Newmar Dutch Star 3803. The in-dash radio (Sony with removable face) does not have power regardless of what we do. So, I want to take this opportunity to replace the head unit with a large-screen (9-10 inch) that has CarPlay connectivity for maps, music, etc.

I went to our local car stereo shop (has been in service for 30+ years…I mention this only to say they’re not a fly-by-night and “should” have knowledgeable technicians), and their technician said something about he would need to take out the existing unit and look at the harness to a) see if he can even install a replacement and b) if he would need to use a standard harness or custom build a harness.

I have a few questions:
1. Has anyone replaced their stereo? Was this Sony a likely factory unit?
2. If replaced, was there an issue with the wiring harness?
3. Has anyone here replaced their “standard” radio with one of these larger screen units in a model of this relative age?
4. If I replace it with one of the larger screen units, will I have a problem powering the new unit? I understand that the stereo is powered by the house battery bank so that it will stay on when the chassis is off since it runs sound through all the speakers in the coach, front to rear.
5. Should this be a problem to install given the heavier weight of the screen? That is, is there enough “support” behind the dash to mount/support the radio body to the chassis?

Thanks in advance for everyone’s kind responses and help.

(FYI, I’m also posting this same thing in the Newmar Owners area)