I just performed this job on my '87 300TDT last weekend.
Didn't complete the job in an hour, but I'm quite a slow
mechanic. I'd starve if that was how I made a living...
A few tips. Access around the thermostat housing is rather
tight. You can remove the two housing bolts, and even work
the thermostat out, but won't have enough room to install
the new part. I found it best to remove two parts to make
room to work. First the large rubber hose which feeds the
turbocharger from the air cleaner. A simple clamp on either
end can be loosened with a philips screwdriver. Second,
there is a temperature sensor threaded into the block
directly in front of the thermostat housing. Just unscrew
it - you're at risk of cracking the plastic parts when
attempting to work around it.
I changed the coolant, so I can't tell you how much to
drain - I don't like inhaling/showering/laying in
ethylene glycol, so I got it all out first.