1998,How much to replace an automatic transmission to a manual

I have a bmw automatic transmission and it grinds on 1st and 2nd gear and after it reaches speed its fine. but i wanted to get a new transmission so i dont have to deal with it always stalling, but i always wanted a manual car so i was wondering since im replacing the transmission anyways would converting the car from automatic to manual be too much money and a pain?
My car has an automatic transmission.