Basement specs from builder

I have an unfinished basement with 2 standard little windows. If I want to finish two bedrooms, I'll have to install egress windows. Correct? My question. Is this something that is a possible do-it-yourselfer can do, or is this something that is best left to the professionals? I went to a home store and saw egress windows for about $100-$125. Does anyone know the price that I would be expected to pay to have someone replace the two windows and install egress in their place? The basement is 100% poured concrete. It is not a walk out or daylight. Thanks!

I have an OLD Stone home. The basic footprint of the home is rectangular, with all four walls of stone and the gable ends being the short sides. (looks like a typical colonial home) The interior wood framing that supports the floors and central staircase consists of a large beam 12 x 12 that extends from the center of one gable end to center of the other gable end. perpendicular to this beam are the floor joists which are 3x8 timbers, set into slots in the stone wall and mortised into the main beam, spaced about 24" on center with the exception of the area that underlays the stairwell/center hall. On either side of the Hall the joists are 4 X 8 timbers with a 7 foot span between them. (this allows a large enough area up through the center of the house for the stairs from basement to attic) on top of these Jumbo Joists, rest the walls that separate the rooms from the hallway. The walls are constructed with 12-24 inch wide planks one inch thick set side by side (like exterior sheeting) resting on the floorboards (and jumbo joist) and face nailed to the joist above, then covered with wood lath and then plastered. The wall for the floor above is similarily built. It is on of these Jumbo Joists in the basement that have broken. It snapped (probably 50 years ago) near the center of it's length where a crosswise member is joined to it with a through tennon joint. (the cross member is one of two present along its 7 foot length and they provide support for the hallway floor above). How can I repair this broken structural member? I can't replace it because I won't be able to lift the wall above out of the way to get at it, and I won't be able to slip a new one in place anyway because of the 2 through tennon joints that will need to be put back in place, not to mention that I need to slip one end of it into the support built into the stone wall and the other into the tennon cut into the main beam of the house. I was thinking of sistering it with a beam of the same size, but I am not sure of how to join the two, or how to join the new beam to the main beam of the house for support. I figured that the end that would normally go into the stone wall could be supported by a lolly post so long as the support beneath the post was set up to distribute its load across a reasonably large area of the basement floor(concrete). I also thought about jacking it back up to nearly level (depending on how much the plaster cracks - I know that I can only lift it about 1/8 inch per day at the most) and then supporting it from below with a small steel I-beam, with posts set at each end of the I-beam. (this will keep them out of the way of the useable basement space that I have) BUT I am worried about the I-beam just sitting there on top of the posts and squeezed between them and the joist. Will I need to secure it in some way from twisting or sliding one way or the other? The Jumbo Joist that needs to be repaired looks like it was hand cut by a sawyer 200 years ago when the house was built, and I doubt that it is a perfectly level surface that can provide even bearing for the I-beam. I hope that some of this makes sense. Thanks for taking the time to read this and for any information that you can give. HB