i'll have to ask my wife how important the heated seat is
Ok... with this strategy, you've already lost the battle. Because as soon as you 'ask', you're going to be the bad guy if you don't do it quick like a bunny.
The only answer she's going to give is "yeah, that would be nice to have" (and tbh, you'll say the same thing, once you've got it working)
Rather, turn this around to your advantage. Tell her you found out the driver's seat should be heated as well, and you are going to find the parts to re-enable it. Win for you.
Even better, you'll have all the time you need (although to have it working by January scores you bonus points)
It's all about messaging...
Now, on a more serious note... easy way to check, before searching all over for a driver door module (DDM) ... pull the switch assembly from the p/s, and use it to test the connections on the d/s. If the seat starts getting warm... you know that's all you're going to need. Don't pull the connectors with the heaters 'on'. Turn them off, or key off, before disconnecting the switch, to safeguard against shorting out the switch (and having to then buy a replacement for the p/s).
Actually, the DDM you need
may be longer than the one you have now, without the heater switches, and if that's the case, the armrest in the door panel may have a different cutout (to which, you can either find the matching door panel, or get enterprising with adapting the existing armrest to fit the larger switch.)
It's been awhile since I messed around in that area with my Envoy, so I don't remember if the DDM assembly can be pried up with the door panel in place, or if it has to be removed (on my full-size pickup, the door panel has to come off; I had to clean the switch contacts on it, recently).
I do seem to remember there are two latches on either side of the 'long' ends of the switch. Use a trim tool, and be careful. Also, find a picture of one online, so you get an idea of where the latches are, and how they connect.
If you get a 'brand new' switch assembly, it has to first be programmed / initialized with a high-end scan tool, thanks to the way GM did these things, back in the day. But a used one will already have been done -- another reason for you to get one of those, besides being cheaper. Junkyards and online sources like E-bay and car-part.com are your friend, here.