I think #320 is in the range of 2018 MXRs that can potentially have a higher risk of having the wire-bond issue (does anyone have the range list handy?). However, that being said, very few bikes in that range will ever develop an issue, so I don’t want to discourage your purchasing decision. Also, even if you develop the code 36 issue, you can still ride the bike.
I was in the same boat. I bought #361 from a dealer for the same price you are looking at paying, knowing it could have some issues down the line. In retrospect, it was way over priced. But I wanted one, and that was the one I found. And I have been super happy with it.
I think you might have some more options now, as a few bikes are coming up for sale in the $7-8k range that have a few miles on them. If you are looking for a streetable bike, go with the EXR. In some states you can make the MXR road legal, but some you cannot.
I would definitely suggest building a laptop with Multitool and get the data cables. That way you can check out potential bikes and work on your own bike.
@TCMB371 has some excellent instructions on doing this. You can always sell the laptop and cables later if you don’t buy the bike.
Also, make sure the bike has latest firmware, and make sure the bike charges before you buy. Nobody wants to get home with their new electric toy and be unable to charge it.