I have 3 small basement windows in an old concrete block basement wall. They have old glass in old metal frames and don't function as windows and we don't care. We'd rather seal the openings up completely with glass blocks.
Each window is no more than 12" tall x 30"wide. There are traditional leaf-clogged bug-infested window wells outside each one. They let in barely any light, they don't open, one at least is cracked, and one in fact actually has an OLD metal exhaust fan mounted in it, not glass.
I have not shopped yet for materials, and I have no experience, so I'm not sure if I'm in over my head already. For example, what do you do on a project like this if "standard" size blocks don't exactly fit inside your opening? I'm not sure I want to tackle cutting glass blocks!
Is this a project a reasonably competent DIYer could do, with products bought at, say, HD or Lowes or equivalent? It's hard for me to imagine any contractor would find a dinky job like this worth his time...
In my area both HD and Lowes have preassempled windows available as well as the ability to have them made to size by a local supplier. It's a DIY project but unless you have some experience working with cement you might want think about getting help from someone, friend, neighbor, etc.
A premade window requires good measurements. The easiest way is to have them made up. Knock out the existing window and frame and then insert and shim the new glass block window in place and then cement around it using a bag to squeeze in cement on both sides. Remove shims and finish with a trowel.
As a reference a 16X32 window in my area runs around $45 - $60 each. Installed, complete with removal of your old windows can be $130 - $150 each.