More newb questions

I started to take off my headers today and when I took off the first bolt, water started pouring out. At first I thought it was gas, which was also puzzling... but it was definitely water. When I took off the valve covers I didn't notice any water in there. The head gaskets are bad, but there's no peanut butter in the coolant. Granted, the motor has probably only been run for 15 minutes total since I've owned it (a couple months).
Is this something that might be catastrophic or just pull the heads, replace the gaskets and keep rolling?