New-to-me car. Having an issue with the central locking.

Symptoms:
- key works in door, trunk, and ignition.
- remote button on key operates the immobilizer - changes the red/green lights in rearview mirror
- trunk release button on center console operates trunk correctly
- door lock/release button on center console works
--HOWEVER key fob button does not open/close all doors - only does immobilizer

I've had Willy's of Great Neck, NY (widely regarded as an MB Wizard) look at the car and tell me that I need a new key, but can only get one from a stealership.

So, I stopped by MB Manhattan (on 11th Ave in the fifties,) last week and jumped through all their hoops to get a new key ordered, and was promised that I should get a payment link via text or email for "about $300" which would fire off the order process.

It's almost a week later and I've heard nothing. So, I called parts and spoke with the same droid (who shall remain nameless) again today, and it was a Marx bros-esque comedic cluster.....
>breathes in and out several times...<

It was an interesting customer service experience, and a joy to be able to teach a twenty-something drone about some basic customer service techniques. After not being able to find my order, and then not being able to find me in the system (he photocopied all my documents last week and I watched him enter all the info into the system), we had to resort to the VIN number for him to look the car up and then tell me that... "that key is on backorder with no ETA."

And that seemed to be it.

End of story.

It was like trying to get info from a clam above the high tide line, but I finally managed to wedge a knife into his understanding of the situation and offered one of two possible courses of action on his part - that he either ask his manager how to solve the problem for the customer, or that he call his distributor / the factory and find out whether they planned to make any more keys. I'm fascinated to know whether I will receive a callback tomorrow.

All of which is something of a digression, what I really want to ask here is....

1. Is this assessment of the problem likely correct?

2. Is the Manhattan, factory owned, dealership always this bad?!?
3. Any recommendations for a dealership with a few more braincells in the parts department who will charge me LESS than $300 for a key. One key. For what can't be a particularly high tech key... yeeshk.
4. Any third party options to get working central locking?

Thanks in advance for any pointers!