How much is it to replace a front pump seal on transmission 77 Monte Carlo

 

About $15 for the seal and 2-6 hours of labor. If you do it yourself, labor is free.
By the way, if the transmission front seal is leaking, you can bet that all the other seals will need replacing, so, may as well replace those seals while the transmission is out.

 

What does that typically cost to replace the seal?

 

I spend about $15 and do my own work.
For a "typical" cost at a shop, ask your local AAMCO. For a reference to a competent trustworthy transmission shop, go to a local car show, cruise nite or cars & donuts cruise – places where old car guys gather – and ask them.