Heater core-no AC, late Abody-- how much of the dash do you have to disassemble?

Spent a little bit of time armwrestling with my long-dead heatercore in my non-AC, '73 Dart Sport.

It appears that it will put up a bit more of a fight than I had anticipated.
has anyone done this job lately? How much disassembly did this require?

Thanks for any tips!

PS- will a replacement from Rock Auto or Napa likely work? I recall some guys having fitment issues when replacing theirs...not sure if this was a universal problem.

Thank you greatly for any insight!

:prayer:

-Mike