Keith, For the record, and maybe this will show up in a future search to help someone:
To replace a circulation pump on a AHE 100 04s, do not try to remove the bracket to which the pump is mounted. Use a stubby (or ratcheting right angle) screwdriver and remove the 3 screws that hold the pump to the bracket. When installing the new pump, attach the pump to the old bracket with a ty-wrap or two.