thanks to all who provided advice. i'm happy to report that i succesfully and without incident changed four pads. the technique i used was the first one i received, which came from dennis stover:
take a flat blade screw driver and shove it behind the brake pad, at the open end of the holder. The pads pop right out.
i first put the screwdriver between the pad and the closed end of the shoe to push the pad out a little. that made it easier to work the tip of the screwdriver in between back of the pad and the shoe at the open end. after that i tapped the screwdriver all the way in, with the shoe resting on a piece of soft wood to prevent damage. by the time the screwdriver was all the way in, the pad was half way out. i twisted the screwdriver and out popped the pad - with absolutely no damage, widening or deformation of the shoe.
i did not have a chance to use ted ernst's advice to use alcohol, but i'm sure it would have made removal even easier. insertion of the new brake pads was basically a reversal of the process. i lubricated the back and sides of the pads with saliva (it was handier than the alcohol), slid them into the shoes and finished with a couple of mallet taps. success!
thanks again to all, especially dennis stover
ray dobbins
miami florida