What are some difficulties when switching from trombone to bassoon?
It's an entirely different instrument, and are in different sections. You're going from brass to woodwind. Basically, you're starting from scratch.
good for you. i switched from drums to an alto-horn, and then taught myself to play clarinet. you are in for a real treat. the woodwinds are beautiful instruments, with a different feel, wood instead of brass, softer harmonics and scales then drums and brass. try the classical music scores, wonderful things. https://www.youtube.com/watch?v=fIAMXocEk4E