You probably will need professional help on this one. Anytime you have to cut or break concrete you are venturing very close to te point where DIY is no longer appropriate. Not that it can't be done, but there are possible risks to the structure of the concrete, it is a fairly difficult job without proper tools and know-how. It is almost impossible to give specific advice on something like this without being on site to examine the entire picture. It would be wise for you to consult local professionals before proceeding.