I don't think you need a formal post bacc. I'm a non trad (nurse) that had none of the prerequisites other than gen chem I. I enrolled myself into my local school and took classes part time while I worked over a period of 2.5years or so (I guess this would be considered an informal post bacc). I didn't need GPA repair though, so if you do I would sit down and talk to the premed advisor at a local college. The formal post-baccs are very expensive if I remember correctly because I initially had looked into doing one. If you start taking classes now at a full time rate and go through the summers, you could maybe apply for the 2021 cycle, if that's too quick than shoot for 2022.