I'm afraid that the drive will probably need to go to a data recovery service.
If it isn't detected when you plug it it, the chances are that the data is ok, but something in the circuit board has failed.
Most of these places have a stock of old drives. The first thing they will try is simply replacing the circuit board on the underside of the device. If you could find another drive of EXACTLY the same make and model, you could try that yourself - it's a relatively simple task. You simply unscrew the board, remove the ribbon cable, and reconnect the new one. Try searching the net for the exact make and model.
Be careful though, as there can be different revisions within the same model - you must make sure that the revision number is the same as well.
It's possible to transplant platters, but trust me - it is an incredibly tricky and difficult job, for which you would to do a lot of research and also special tools to keep the heads spaced apart. Without this, the job is practically impossible, and on a first attempt, I guarantee that anyone will destroy the drive completely.
Transplanted platters don't last long, either - maybe long enough to recover the data, but it's not a permanent solution. I don't recommend doing this at all!