If you gai through the work of a new window, make sure the window intself is certified to ne an "egress window". All munufactueres know the requirements.
As far as the location of the window, you local building code people can steer you to the proper heights for the window to qualify as an egress window. The most critcial dimension is the finished sill height (not rough opening height in the cobcrete) since this can vary slightly from city to city. This is to permit childern to get out.
Do it right because you will appreciate it when you go to sell, since you will have more qualifying liveable area to base the appraisal and the buyers mortgage on.
If the amount of concrete cutting is substantial, many people find it is better to find a concrete cuting/sawing contractor that will do the job very quickly with little mess and get rid of the debris. Make sure you give him the proper locations and dimension of the rough opening.