[kaptain]

I would want to verify something before I allowed that shop to have any more of my money.

Will the coach air up in LEVEL mode? If it does, then air bags are NOT the problem.

Excellent suggestions and questions.  I could not test and did not ask the shop because I was afraid that question might irritate them.
I'd guess they'd most likely say "yes of course", otherwise we wouldn't email you on Thursday, June 23 saying "the service work is done and RV is ready for pickup."

I could not test this myself because I and the tow truck driver was never able to re-start the engine - dead batteries.
We tried various ways to restart - including jump start using my truck, my "NOCO Boost Pro GB150 3000 Amp 12-Volt UltraSafe Lithium Jump Starter",  jump start by AAA road service (3rd party), charging using jumper cable with the tow truck(big semi-truck), etc.. all failed. I notice this high-capacity battery pack drops quickly from 12v to about 8V, at this voltage, cranking it all you get some clicks, but not strong enough to turn or start the engine.

On the day of picking up the coach Tuesday 28th,  after the tech charged it for 15 or 20 minutes, the engine cranked/started, after another 15 or so, I can see it airs up and leveled. The battery charging took a while as the tech initially started with a battery booster that didn't seem to budge, later he brought a gasoline-powered charger, and waited charging for 15 or 20 minutes before the engine cranked/started.

The towing distance from where the coach was parked from the shop was only 3 or 4 miles. The cost for towing cost I heard was like $2600, it took them a while because the tow truck company was trying to get (additional) cost approval from my insurance.  Fortunately, I did not hear from my insurance that I must cough up some $

When I first smell smoke until I stop was like 2 minutes drive, initially thought its something outside not my RV. 
This means the RV lost leveling and start to lean very soon I drove out shop's parking lot. When the tow truck arrived a couple of hours later, the engine could not be re-started as the batteries were dead. 

After reading your suggestions, I was thinking to try to start the generator, but not enough battery to start anything. All battery terminals (without disconnecting or re-connecting anything) were measured to be about only 4 volts. So starting the generator to charge or testing in "LEVEL" mode was never possible.

The initial service request includes works for checking air leaks and replacing airbags. I ordered and dropped shipped to them 4, they only used 2, leaving 2 unused in the storage tray.  I ordered 4, one time from Germany and 2nd-time from Poland because the shop could not find them within the USA or from Newell. The 1st order came from Germany supposed to be complete sets, but that didn't come with a top base. Re-ordered from Poland came in as complete sets (bottom & top metal base, piston, rubber sleeves).

Ask the tech at the shop, WHO he has spoken with at Newell?

I'll ask them about this and update you once I have that info.

Is this a shop that normally works on Newells?

This shop specializes in servicing chassis and suspensions. And was one of the shops I found online that described services for various RV models. I believe one time Newell had a service directory that included this company. To avoid causing potentially publicity or negative perception, I will not post the name of this shop but I can pm you.

Photos showing both engine battery and house battery are exact same 4 volts = this seems to me to infer the two group batteries are already "MERGED". 
Since I never, nor did any of the tow truck drivers touch the battery MERGE switch, I'd guess the batteries already set MERGE at the shop. Am I making wild assumptions?