DimeBlazr:
I hear ya on the Blue Devil stop leak. I researched it pretty good before I used it and I understand the risks. Yet, I know it has helped out on certain occasions and in specific situations. I used it in hopes of stopping a frost plug leak knowing I would be doing a coolant change shortly because I was going to replace the water pump and lower radiator hose. I didn't anticipate a heater core issue at the time. Probably, because I was expecting to be in Florida at this time. However, now it looks like I will remain in Minnesota, so I think I'm gonna use the heater a couple of times. In fact, it is 12 F degrees right now with a 0 F degree wind chill. We will actually hit Zero degrees tonight. Problem is, it is too freaking cold out to work on. Don't have a heated garage. I will check the heater hoses more closely and go from there. Also, plan to recheck the frost plugs and gaskets again soon. No signs of coolant in the oil, which I will watch closely. I plan to change oil again before it really gets cold up here.

To everyone who has commented,THANKS for your response.