Am I Screwed?

Alright so I play the bass for my school's jazz band, however, we have around four bass players which is a tad overkill for a 15-ish person band. So my band director is having the bass players learn another instrument over summer break. He picked me to learn the trombone and gave me about like an hour of instruction on how to play before just sending me on my way with a trombone, some slide grease, and an instructional booklet from 2004. He doesn't expect me to "magically be a professional by next year" but I'm still worried that I won't live up to his expectations for the band. Like I can remember my positions and my embouchure is okay but I'm worried that I'm not going to progress enough by myself and with the book, I also don't have the time or money currently to get a teacher. Any advice for me?