Thanks all for the tip. I ended up just replacing the good piston seals and piston, hooked it back up to the brake line and put a block between the good piston and pumped the handle till the old one came out. It was pretty scratched up from my prior attempts with the pliers so I bought a replacement piston.
Here it is just after removing the caliper
Then finally out! You can see the gnarled piston in the background
Left caliper before:
Left caliper after:
Funny, the left one went so quickly and I didn't really have to reference the guide or the manual. Just did it [emoji106].
Bleeding the brakes didn't work so well the first time, so I did it again, and things were cool.
Thanks for all the tips and this guide, John. I can now say I've done brake work! Very satisfying to do it myself. Saved [emoji385][emoji385][emoji385][emoji385] too!
Here's the ride before I took it out with new brakes:
Again, thanks all!!