Extractor Heater Update
Tore this baby down this morning. Removed the in-line heater and took it as far apart as we could, which was not very far. Looks like it has a thermostat siliconed in place, the whole heater element is sealed, etc. Not designed to be repaired but replaced.
Wound up buying a bucket heater at Agway for $44.99 + tax. Had to get a new section of hose made to bypass the original heater, another $23. Re-installed new hose, dropped heater into tank. Bingo. All fixed. Thanks for the advice!