Coolant Leak on 1997 Pontiac Grand Prix GTP

I've been having a couple problems since the winter rolled around. Coolant is leaking and I can't find the leak anywhere. It's over heated twice. I can't even drive it a mile down before it starts to over heat. this is after putting more coolant in. I'm also noticing a strange whirring coming from my belt and I think that needs to be changed too. Any idea about repair costs for either problems and what to do in the meanwhile about overheating.
I don't know much about cars, but I got this Grand Prix in
June and I think the previous owner may have purposely over-looked some issues when selling it to me. I do love this car though

Asked by for the 1997 Pontiac Grand Prix GTP
The whiring noise and coolant loss sounds like the water pump behind the timing cover is leaking and geeting coolant on the belt. You might not see it leaking while stopped because it might be coming out while under pressure while driving.
2 answers
We recently had a customer with a 2000 Impala and they had coolant "disappearing" and it was due to a leaky water pump...I would start there as well.