Welcome to JA!
A replacement transmission will work from 1986 to 1995.
Yes the transmission will have to come out to fix the leak.
Most of the time its about 4.0 hours to remove and install the transmission.
and about 1.5 hours to fix the leak you have.
If your pulling the transmission this would be a good time to check the clutch too.
Let me know if i can help more!