I've had some good luck when swapping circuit boards on hard drives. I once had a drive with a damaged circuit board. I happened to see on Ebay an identical drive that had the click of death, so on a whim I bought it (for under $10, I believe). Swapping the circuit boards (which was really easy, given the right screwdriver) resulted in one good drive and one entirely dead drive.
You need to be sure that the circuit boards are compatible, which is best done by getting exactly the same model. Sometimes a slight model number difference doesn't matter, but sometimes it does. It's a bit of a gamble.