Cost for rear-transmission seal replacement on 1994 Chevrolet Astro

My '94 Chevy Astro Cargo Van is leaking transmission fluid, I've been told by multiple people that it is the rear transmission seal. How many hours labor should this take, and how much should I expect to pay for going to a mechanic?

Asked by for the 1994 Chevrolet Astro
The book time to remove and replace the extension housing seal is .8 to 1 hour plus the seal cost ($5 to $10)