Organ tech's love it when the untrained try to fix Leslies! It can add several hundred dollars to the bill!
Get a tech - he's worth whatever he charges.
BTW - there is not enuf information in your post to even guess at a diagnosis... What model Leslie? - really makes a difference! Older models don't have choral. Some Leslies have upper and lower rotors, some only have lower
Also, remember that the upper rotor turns at 400 RPM! It won't take a finger off, but it will break one just fine! (The lower can do this also...but normally has a dust cover, which will limit how much you can get hurt - hopefully.)