Full time Rural Carrier thinking about quitting

I'm starting to think of this job as a big dead end. Pay isn't keeping up with inflation. Plus, being trans in a red state is rough, and the prospect of postal service privatization is unappealing to me. I want to move on.

A couple of questions:
How do I quit as a full time carrier?
What happens to any remaining annual leave? sick leave? retirement account?
Thanks a lot!