Dress warmly. LOL. Otherwise below are some tips to consider. Common issues I dealt with while supporting construction equipment diesel engines mainly in Canada and Great Lakes. Probably overkill but go as far as you'd like. Real talk: If you can park the car inside, that'll solve most problems.
A diesel heater would be awesome to add but I guess you should decide if you are willing to spend that. If you plan on going to cold climates in the future often, YES.
Check your glow plugs. Easy way to check, if you have a laser temp gauge, turn on the glow plugs and shoot each glow plug. If you have a "low" reading glow plug, then you have a bad glow plug. Interwebs says get legit BOSCH glow plugs for bestest performance. Also book says glow plug from 10-15 seconds.
Pull your heater core and have it flushed if it hasn't been done. My heater core was straight up clogged and cleaning it out made all the difference. Make sure your defroster works (aka, the hoses are still attached)
Are your door seals in good shape? If not, this is an easy fix to make life better.
Radiator muff. YES (also I've done the "cardboard" and that doesn't seem to do much. Or maybe I did it wrong, either way radiator muff is good, the RN radiator muff seems to be super solid).
Synthetic fluids in engine, transmission, transfer case, and diffs. Dino fluid will not like the bitter cold.
For the oil pan heater, if you are able to plug in, yeah sure. Any heat to help get a diesel engine started. It won't really (or at all) heat the block and won't make for easier starting, but will allow the oil to flow easier and build pressure. A true block heater would be better but that can be a project and I'm assuming you aren't flush with time. But the flow of engine oil faster at start up is beneficial for longevity of the engine.
Fresh fuel filter(s). On the way out there, run some Standadyne fuel additive through your diesel fuel system. Cheap and easy fuel system maintenance. Diesel fuel there should already be winter mix, so should be good to go on that front.
Properly adjusted and working parking brake (stay with me on this)
When warming up the vehicle, when its idling after start up, select neutral on the transfer case and a gear on the transmission (I forget what the book says, but I think 4th??). That way while the engine is starting to warm up, the gears are starting to move and the oil is starting to warm up and lubricate the transmission and transfer case.
Also when idling diesels like the TDI300 in extreme cold, if you think you are going to idle longer than 15 minutes, shut it off. On start up, let the engine idle for no longer than 5 minutes then start putting it under load. At 5 minutes, lubrication is happening quite well and its beneficial to put heat in the engine. No engine heat leads to wet stacking (unburnt diesel fuel getting into the turbo and exhaust). A little can be ok but it can clog up an exhaust system. Seen this happen many times with industrial diesels.
Cheap windshield cover like this. Just makes life easier:
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Good ice scraper with snow broom
Fresh wiper blades. Also make sure your windscreen washer works. Also filled with correct de-icing fluid.
Strong battery and battery blanket. If your battery is 4 years old, its going to start to show its faults. A battery blanket will allow your battery to stay warm. Cold batteries do not work as well.
All of this is overkill but I'm to the point in my life, I'm not going to be inconvenienced and my engines/transmissions are going to last as long as possible. So that is my point of view.
