Tele_man:
Here is the list of TRS-80 references from the catalog:
Subject: TRS-80
Clev: I bought mine from Napa Autoparts. I am pretty sure it is the exact same part number as mine as for your Accord, but I looked it up through their site to be safe.
They carry two models, one by Balkamp (what I got @ $49.59) and one by Kats which is cheaper (@ $37.99), but didn't look as appealing to me. Both are the same wattage (400W).
Here are the links:
Balkamp Heater
Kats Heater
On my engine, it just replaces the coolant drain bolt, which is just above and to the left of the oil filter and somewhat recessed. If your engine is similar to mine (F22A1), it should be in that location. I just recommend having a mechanic you know remove it for you to save time and blood. Of course, the antifreeze needs drained as well.
Two and a half hours plugged in seems about optimum in current weather here (~40F mornings), but the colder it is, 3 hours may be better/necessary for the equivalent benefit.