More mixed news today while the shop was still closed.
I went and tried the transmissiont this morning after it had gone cold and the transmission was extremely noisy but would go into gear, so it's not completely dead, just,
unwell. Still no indications of particles in the fluid, nor does it look burned which is good.
I also dug through a bin of parts that the previous owner had and found the original AM/FM/cassette unit, which no longer fits as the opening had been widened to fit a standard car stereo head unit. There was also a lot of odds and ends for trim pieces, the dome lamp withe dual map lights and little replacement parts that will come in handy like a new lock for the ignition and the drivers door but more importantly I discovered this car is equipped with Cruise Control!
I could not get the cruise control to operate while I was driving however now that I know what the peculiar yellow box I restuffed under the dash was it may simply be a disconnected wire or vacuum line.