1 - it's normal, water pump activates as demand requires it, it's under the floor and it amplify the noise i guess.
2 - if the buzzer noise is what you hearing, look at the "travel warning", to the right of the steering column. if it lights up when you hear the noise, it is either the step, awning or the leveling jacks. (leveling jacks will auto retract as soon as you drop the hand brake)
For MB related issues, always go to MB.
3 - look for the dometic stove manual in the bag, it's probably a simple fix.
4 - this antenna is meant to be used with PepWave LTE router.
this is the one that will utilize dual wifi + dual celluar + GPS signal
Airstream charges $1k for this device, and is limited to AT&T service.
I bought my own, and added a data only line to my Verizon account.
simple setup. all the wires are in the rear center overhead cabinet, it's tucked to the driver side. plug and play.
5 - it's a Onan 2500 LP , there's a Onan owners manual in the bag
6 - https://www.airstream.com/owners/manuals/
, around page 110
7 - I think the Zamp is for solar to engine battery, BatteryMinder is shore / gen AC>DC for engine battery. both are under the driver seat. (both of mine are from BatteryMinder) 1 of the 4 solar panels, is for charging engine battery
if you really need some help, call the service dept and speak to a tech directly, they are usually friendly and helpful, or speak to the tech who gave you the delivery walk-through.