You can do it yourself.
Anybody that knows 'hardwired' and observed timer is making humming sound can wire up a timer.
If M88T timer dial is not rotating, but power pack is making humming sound, then that says timer is receiving power but clock motor has gone bad.
There are no replacement clock motors for power packs.http://waterheatertimer.org/Malibu-power-pack-stopped-working.html
To wire a new timer:
Click circuit breakers until the humming sound turns off.
Turn breaker back on to confirm that humming sound is associated with that breaker.
Buy a tester at local hardware and ask them how to use it.
Tester will give you assurance that power is off when connecting new timer.
Outdoors: put down dry boards to stand on, never stand on bare soil or wet/damp surface, don't touch anything metal and don't hold metal screwdriver in mouth while working on electric circuit. Wear gloves if you want. And don't sweat.
With 120volt circuit, as long as you are not grounded, which means that you are not touching soil, or anything that grounds back to soil, then you will not get electrocuted. You can get shocked only if power is still turned on at circuit breaker, and it will be surprising, but it won't kill you as long as you're not grounded. All electricity goes back into the earth to complete circuit.
Open the box where timer is hardwired.
Use tester on black wire. To confirm power is off.
Typical 120volt circuit: Black wire is Hot and carries voltage. White wire is neutral and completes the circuit back to ground. Bare copper wire is ground and serves as redundant safety.
Old 88T timer will be wired black-to-black, white-to-white, and green-to-bare copper.
Take photo of wiring to avoid confusion. Post photo on flickr and add a comment with link to photo for another pair of eyes on situation.
Cut off end of new timer wire, strip insulation with knife and attach wires same way previous timer was connected. http://waterheatertimer.org/How-to-twist-electric-wire.html
To install ordinary 120Volt outlet so timer can plug in: Buy outlet from hardware: Black hot wire connects to brass-colored screw, white neutral wire connects to silver-colored screw, bare ground wire connects to green-colored screw.
Open following link to see basic circuits:http://waterheatertimer.org/B220C.htmlhttp://waterheatertimer.org/See-inside-main-breaker-box.html