We have a bad garage floor at the garage doors in the sense there are chunks of concrete missing and cracks of various sizes. We need to replace our old wood garage doors with new steel, insulated doors. I can avoid most of the bad concrete by moving the garage doors two or three inches inward into the garage. This possibly could be done by having some of the framing around the door wider so it extends several inches further into the garage. Thus I replace a concrete job with a carpentry job. The bad concrete would be visible when the garage doors are shut, but I can slowly do repairs over the years. Otherwise I have to find someone in my area who can do good concrete work to make the repairs before the new doors are put in. Is this reasonable?

do i have to rent a machine to do this? if so what's it called or will staining the floors alone do the job? any info is greatly appreciated