Wish I had an active subscription, I would help you out. Otherwise, you can sign up for a 1 month subscription here for just $20 and get all the diagrams/instructions you need.
https://www.alldata.com/diy-us/
I would figure out a way to check the sensor, or the reductant level sensor may be malfunctioning or damaged, causing the P203E code to be triggered. Inspect the sensor and wiring for any signs of damage or wear.
Welcome Jim.. at this point. Do what makes you the most comfortable.. with no warranty, make sure you're prepared for the worst in case you're one of the unlucky ones.
The trend right now is EV for sure.. but, still years away. Either way, these motors will last forever and be one of the best you've ever had, or the worst. There really is no in between sadly.