3.5" Drive Problems

[jhack@unixg.ubc.ca (Jeremy Hack)]

After 9 years of dedicated service, my 3.5" Apple drive has quit
working.  This happened after I moved it from one side of the computer
to the other (no substantial force whatsoever), so I think it was 
probably ready to go.
 
The symptoms are:
   - makes a constant "chugga-chugga" noise when power is supplied
        (ie when computer is on, even when drive not being accessed)
   - recognizes a disk insert, but goes into an "infinite loop" while
        trying to read data
   - pressing the eject button (after I get the drive light to go off
        with a ctrl-reset) results in a multiple eject (usually around
        three).  The disk is ejected on the first try, however.
 
I opened up the drive, and saw that the "chugga-chugga" noise was
being caused by a pin (coming from the read/write head) slipping off
the threaded post turned by the motor.  It only seems to slip when the
pin/head is all the way back (accessing outer part of disk surface).
Is this even supposed to be turning when a disk isn't being accessed?
 
Is there an easy fix for this, or would I be better off just finding a
whole new drive mechanism?  (I could put a Mac internal drive in the
case, right?) 
 
Thanks for any help/ideas/suggestions =)