go to an auto parts store with your car, or with the removed alternator. they can compare them to make sure they are same. they will also want to keep your old alternator to rebuild it.

many years ago i had to replace my alternator. the guy at the auto parts store was a friend of mine. he put the alternator on a machine, tested it, disassembled it and replaced a diode, all in about 10 minutes for less than 5 bucks. this was for an 88 buick.