Recommendations for Replacing Bricked Over Basement Window Openings?

Hi All.  I have two former window openings on the rear, basement wall of our brownstone which were previously bricked over and the wells were haphazardly filled in.  They are now crumbling and and I’d like to replace them with small windows and an appropriate well on the outside to ensure prevention of water infiltration.  I had a mason come and look but I was not sold on his confidence level for doing the job.  Does anyone have a similar experience with this as well as recommendations for contractors?  Thaks!