Bryan, best wishes on all your troubles which are so much less than heart surgery, as you said.
Your car troubles bring back memories galore of a previous vehicle, whose engine light was always going off. I kept finding new parts they had put on the car that kept going bad. I found that I had a MAP sensor on the car, which I didn't know I had, but when it didn't work, the car didn't either.
I replaced the O2 sensor myself. The dealership wanted $85 to replace it, but I knew I could do better. I went to my local NAPA dealer, and bought the part for only $60, and came home to put it on. But there was this wire coming out the end of it, which made all the tools I had worthless for putting it on. There is a special socket you need to remove the old one and install the new one. So I went to the parts store and bought the socket for $25, and it worked great! So I replaced it myself for only $85, AND I have the socket to boot, which I haven't used since.
On that car I had learned how to check the codes myself for what was wrong. I'm not sure that that still works. And I'm probably remembering some of these details sideways or backwards. But anyway, I sympathize with your car problems.