Needs help please!
 

ive bought a 1996 chevy silverado, it has a 350 vortec 5.7l ,and my transmission output shaft seal is leaking. but im thinking my transmission is blew up cause as i was driving i felt the difference it wouldnt like to switch gears and running very high is that just from the seal with a leak not getting compression now its just leaked all out should i buy a new seal and fluid and see or noo is it blew up. thank you please write back with my consern