Sounds like a lot of BS to Me. The "harmonic ballancer" he's referring to is actually the crankshaft pulley as refered to in the Mitsu FSM. And no this pulley does not go bad under normal circumstances. Its pretty much a solid piece of steel with a bit of rubber to dampen vibrations a bit. Have you examined the pully? If it was bad you would be able to tell by looking at it fairly easily by looking for chips in the pully surface or cracks or chunks missing out of the rubber portion (not likely)

What makes the technician (I use the word lightly here) believe that your crankshaft bearings are bad? Do you have a knock in the bottom end?

"I was also informed that the harmonic balancer maintains proper engine timing, lubrication, and crankshaft balancing to promote engine longevity and performance."

Also this statement is almost totally false. Yes the pully helps balancing somewhat, but mostly it "dampens" vibrations from the accessory drive belts which is its primary purpose (to drive the acesorry belts like the power steering belt and the fan belt)

It has nothing to do with timing of the engine, other than the mark on the side to read your timing light off of. Also the pully has nothing to do with lubrication of the engine. It's on the outside of the engine for crying out loud....

Sounds to me like you have a simple misfire. Perhaps a fouled plug or bad coil pack or wire. If you had bad crank berings you would probably know by the heinous sound of knocking combined with a loss of oil pressure....I say this guys trying to take you to the cleaners. Get another opinion and check out your pullly and post pics of it here and we'll let you know if its bad.