Thank you everyone for the feedback over the last few weeks. Using Art's instructions, I finished replacing the cabin fan motor, resistor and impellers. (I passed on the heater core) . My 1993 240 was slightly different, and here are some pics and notes that may help others:

https://www.icloud.com/sharedalbum/#B0eG5VpecbTlwL

- The Volvo radio amp is attached to the bottom rear of the center console storage box. You just needs to loosen 2 x 8mm bolts and the amp will tilt out making it easy to remove the connections once the center console is removed.
- The motor ground wire easily attaches to one of the two grounding bolts behind the center console - no need to splice it to the original connection running behind the plenum.
- Installing the dash board is much easier if one removes the turn signal and wiper stalks from the steering wheel column.
- There are a few more screws attaching the dashboard, and in a couple of new locations - they are easy to find.
- The electrical putty described in Art's writeup can be found in the HVAC section of your local hardware store. Seems that it's classified as 'duct sealer', and it works great.

Thanks again!