Ismalley, you mean you didn't drain the block with drain plug located on the passenger side under the rear-most exhaust manifold? if not, you still had probably about a gallon of old coolant left in it.

As far as distilled water, yes, that would of course be optimal, but tap water is okay to use. It would be very, very unlikely that the gallon and a half of average tap water that you'd use in your system would contain enough minerals, chemicals, salts or acids to do any kind of damage to your system. Unless you change it a couple times a year, I seriously doubt it could do any harm. That being said, I use store bought drinking/spring water.
The antifreeze on the other hand does make a difference. Use only Zerex G05 or MBZ coolant.