I think I'm staying inside this year, save for cooking on the grill! I saw that pile of rockets in the back of
@Doubeleive Denali and decided I better not go near them! LOL
The screen that comes up and goes away real quick is the regular screen. It goes away quick because there's a problem or if you do not have that option. That happens to me when I pull up the amp, side blind zone, etc. Yours is disconnected, bad wire, or broken. As for the digital radio, I get that with our 2004 Montana. The radio works and van runs fine so I never bothered to investigate.
As for the Premium Amp, all the speakers connect to it and then goes to the radio if memory serves. You should have the wiring diagrams for that in your shop manual.