what is the best way (and can it be done) to remix a mixed song

GarageBand 10.1.1

OS 10.11.4

Mac Book Pro

16G RAM

68 YR old hobby recording guy/trying to leave a legacy

What is the best way (and can it be done) to remix a mixed song

I have a song that is mostly improvised, I've been told its cool, however, re-recording isn’t possible.

After reading much about mixing I can now hear where there are uneducated choices and mistakes I made which explains the ‘not quite as good as the song is’ sound.

Before I just jump in and try undoing the settings on the tracks (one is DRUMMER) to get it back to the raw track before effects/eq/compression ect. is is possible to do just that? Open up the unfavorable mix, rename it, save it, and just go to work and undo, or turn off ‘stuff’.

The basis of the poor mix even goes to the root where I have tracks to ‘hot’,( in the orange and red)

I assume by now you understand my question and I am open to positive advice.

Thank you in advance for your help.

jojoguiitar_mn_usa