Yeah, ended up being pretty straightforward, although I'm struggling to remember the details now 30 months later. I've been trouble-free since the fix FTR. Roughly:

1. Underbody panels come off. Tank is located on the driver's side roughly under the driver's seat, maybe a bit farther back where the passenger's feet go.
2. IIRC it has a drain plug. I drained the liquid to save myself on the mess and the weight of unbolting it and pulling it down.
3. The exhaust does not need to come off for this job. It's pretty obvious what you need to do when you get the underbody panels off, although I remember it being mildly annoying (everything went back together without any hassle or needing to mark screws/parts or anything like that).
4. This part I don't remember clearly: how many sensors there are and whether you have to test each one or if it's always the same one that's bad to cause the code. Anyway, there are 2-3 sensors. One at the top of the tank (hence having to remove it to test), one at the bottom, and (maybe) one in the middle. IIRC you take your multimeter and measure the resistance. I think you drain the liquid also so that you can check whether each sensor is offering the right resistance. 10k Ohms is what you want to see. If you don't see 10k Ohms (I believe you just have an open circuit otherwise) then you know the sensor is bad. Again, you'll need to corroborate this with other posts/threads of exactly how to test, this is just a summary of what my (reasonably lazy and inexperienced) approach was and the results.
5. Whichever sensor is bad is the one you bridge. To avoid having a dangling sensor/water intrusion, I took a 10k Ohm resistor and stuffed it into the connector, bridging the two leads of the connector (to be clear: the connector side, not the sensor side. It fits together better that way). This is a tight fit back together because it's not supposed to have a resistor in there... but with enough coaxing it goes back together.
6. Put everything back into its home.

You may be wondering where you get a 10k Ohm resistor. It's not like you can go to a Radio Shack anymore. I happened to have a breadboard kit I bought on Amazon for <$20. But I'm sure you could just buy an assortment of resistors for even cheaper. These are the little guys... the resistor itself is probably 1-2 mm in diameter, and 4-5 mm long. The leads are thin. I just typed "resistor" into Amazon... any of those first hits are fine.

Keep in mind the ECU will now always think the tank is full... so you'll need to be proactive about remembering to fill.