I wouldn't drive it, if the bearings are on the way out it is always going to risk blowing at the completely wrong moment and screwing your engine up.
Replacing a water pump should be fairly straight forward, just drain the system, remove the 3 bolts (i think) that hold it in then slot it out from under the car. Again just reverse to get it back in. Although i would personally allow myself about 3 hours to do it in, just so i was sure that it was all correct and i didn't feel like i needed to rush.