1980 300CD No Heat what to do?

[The Grinch]

I know there is a lot of info on here and the web about the crappy ACCI1 system MB used in these cars. I am looking for input on what should be done with my car to get heat and to eventually fix the system.

First off, here is what is currently happening. My 80 Has NO HEAT. The Blower motor works on def, hi,and low. The AC did not seem to work this summer.
No heat was not a problem this summer but now with days in the 20F range it is really no fun to run this car. Beats riding my motorcycle but not exactly a fun experience.

The car sat unused for 10 years before I got it.

Here are my options as I see them.

1) Go through and trouble shoot the system

2) There is a guy on CL parting out a few 240 D's with he manual setups. He wants 200 dollars for a complete take out with heater core and under dash box and all associated parts.

Problem is it is pretty cold out right now so doing the swap is not something I am looking forward to. I have done a lot of heavy mechanical work including axle swaps, diesel conversions, engine swaps etc so I am sure Swaping the climate control is something I can do.

What would you guys recommend?

Thinking of doing this as a temp fix to get through the winter:
early W123 servo bypass described/pics

Thanks for the input.

Ian