Repair part compatibility question, please help!

Hi! I have a 13" 2020 m1 macbook air (model a2337/emc 3598) with liquid damage on the battery, left speaker, and usb-c board according to the guy from the genius bar. He quoted me $800 for apple to fix it, but theres no way in hell i'm paying all that money for something i can presumably do myself pretty easily. I'm seeing a bunch of batteries on ebay that say they're compatible with my laptop's EMC number, some of them salvaged from other laptops and others appear to be new but third party. Are the third party ones legit, or should I go with a "95% capacity" used oem battery?

Also, the guy at the apple store was really weird and cagey when i asked about the part names of what was damaged. He told me that the part numbers were "confidential", so I also wanna ask here if there's anything else that might be wrong that I should preemptively order and replace in case he was neglecting to tell me something. I'm an art student and need to do 90% of my coursework on a laptop in class, so getting this fixed as fast and cheap as possible is important and i just want to make sure that my plan sounds like it'll work. Thanks for reading, please let me know what I should do here.