1980 300D. Under the passenger foot well and removing the expansion valve.
Bottom two nuts are steel, no problem.
Top two are brass, left side no problem, right side is now round.

So, expansion valve is still in car (original one), brass nut is now rOund.

Since I have to replace the nut I will need to drop the part up in the
dash area.

That is the question - what am I supposed to do to get out the part of the AC
that is in the dash ? I have replaced heater cores before, I imagine it
is something like that.

If you are wondering how I did this stupid thing:
Used a thread release like PB blaster on the fitting threads.
Used a line wrench of appropriate size (19mm).
Rounded the corners first.
Then used a vise grip. This brought the soft brass to round.
Before going to vise grip I tried several wrench sizes to find one with a oh-so-snug fit. I have everything but wentworth sizes.

I could cut away expansion valve, but the nut needs replacing now.
So, out with the AC core .

Can anyone give me some directions ?
Thanks everyone.

__________________
80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250