blocking soffit vents?

If I wanted to enlarge basement windows, would a "window" contractor be the person to do a turnkey job, or would it require one contractor to alter the foundation and one to install the new windows? In other words, I would like to let more light into a basement, so I would like to increase the "height" of the existing windows (current dimensions ~ 2'w x 1'h). This seems simple enough, the window "cut out" in the poured foundation would have to be made deeper, and window wells would have to be installed. Any ideas who to call?

My friend just recently bought a house here in Maryland and it is about 30 years old. We got some snow about a week ago and I noticed some tell-tale signs of heat escaping through the attic and melting the snow on the roof. The second floor bedrooms have partially sloped ceilings to match the grade of the roof and the insulation up there, what there is of it, just wraps around the living space itself with exception of the vertical walls. It doesn't run all the way up to the pinnacle. We are just starting on the process of replacing the old and edcaying insulation and adding insulation that runs all the way up. My question is about ventilation between the insulation and the roof. Since the space isn't going to be used and has vents at either end, is it necessary to put the inserts between the insulation and the roof itself? Any help on this would be much appreciated. Thanks in advance, Chris