My former employer attempted his own core drilling on one of his first jobs. To make a long story short, far short of being done he had broken his own toe and had the drill come loose, swing around and hit his father in-law square in the jaw. Knocked him cold and broke his jaw. This is not an incompetent man mind you. He was just out of his element and under a lot of pressure.
He happened to run into a the owner of the company doing the core drilling for the plumbers (I think) the next day and found out he could get the rest of it done for about what he'd rented the equipment for in the first place.
Hire the pro.
If he's good he might know something about your type of foundation and the the liabilities or lack therof you might face with making a hole in it.
Vince
