Steve,
Place a bucket under your radiator, open the petcock, drain enough to lower water level below the water pump. Remove hoses one at a time & drain into bucket. If you are careful you will not loose too much fluid. There will be some fluid in the heater core so be careful if you have carpet on the floor. Cover with towels.
After repair, pour water back into radiator using a fine screen or cheesecloth to filter the water (to remove any thing that may have fallen in).
