i have a cadillac seville sts 1998. i was driving then all of a sudden the check coolant light lit then a bit after then my car started to overheat so i pulled over and let it cool down and put more coolant then a lil bit after tht all of the coolant that i put in leaked out and my oil percent went from 74 to 0 and i had a puddle of coolant under my car which felt like greasy water i replaced my radiator but then still had the same problems my dad said its either my water pump or a cracked engine block which do you think it is?
Well, the Coolant leaked out because of a broken gasket or pipe or a leak in the radiator or a blown hose pipe. Which inturn caused your Pump to fail, leading to a broken O'ring or Oil seal there, which inturn caused the Coolant you poured in again, to leak into the oil chamber or the oil to leak into the pump casing causing overheated oil to leak out and mix with the already leaking coolant.
Unless you hit something on the road, you shouldn't have a cracked engine block. It might be a decent or saner idea to get the car back home or a garage and hoist it up to check the underbelly, also pour ample water in the radiator to check where the leak is actually from.
If the oil percent went from 74 to 0 you should really check your oil. If it's milky looking then you have coolant leaking in to the oil. Along with the fact you have a coolant puddle under the engine I think it could be a head gasket. The easy way to check is to clean the engine, top up the coolant and pressure test it. You should be able to rent a coolant pressure tester from a store. If you live in Canada then Canadian Tire will most likely have one to rent. Along with what alyoshka had stated I have seen heads of engines warp from overheating. The Northstar engine you have is a good block but if I remember they have Aluminum heads which can warp.