If your car is an automatic, you could have very well pierced one of the veins of your radiator while trying to remove the mechanical fan. If so, you'll need to replace the radiator (or have it repaired/welded by a local radiator shop) they'll charge you like $20. First find out where the leak came from. Did it spray out in a fine mist/stream?
And no, it will be next to impossible to do this with the fan installed. If you can't remove the fan, you have no business proceeding any further. You will harm your car.