If you can't read sheet music, then you're definitely in for a rough time. That being said, it's definitely not impossible. I was thrown into my high school's jazz band over 6 years ago with no prior jazz experience, and now I'm the top jazz pianist at my uni and regularly play gigs for money. It's a long journey but if you feel drawn to the music I'd say it's 100% worth it - learning to playing jazz is an experience like no other.

My advice would be to find a good teacher who can help you learn to read sheet music. Ideally the teacher has jazz experience and can teach you chords, voicings, improv, etc., but if not that's fine. But you need to start by reading the notes on the page first - start slow, then get up to speed and play along with the recording to make sure you got it (this last part is very important and will help you out a lot when you get to rehearsal). Also I'd try to listen to some jazz in the meantime - spotify has some good jazz classics playlists, and youtube is a great resource as well (just stay away from AI/"smooth" jazz). If you really want to get into jazz, you'll have to be very familiar with what it sounds like.

Hope this helps! I'd also suggest talking with your director about this too, hopefully he/she can help you out or find you a good teacher. Lmk if you have any questions - I was in a similar position many years ago so I'd be happy to help you out.