It's really not too difficult fixing your own hard drive, if the problem is a head crash, or the infamous Seagate "stiction" problem, if you know what to do. You will require #4/0 steel wool, paint thinners, WD-40, a few hand tools, and about 45 minutes.
First, you need a clean room, so make sure the garage door is closed before you begin. Move those old lawnmower parts off the bench. Disassemble the sealed unit and carefully wash all parts with paint thinners. Bend the read/write heads out of the way, and then disassemble the platter stack.
VERY CAREFULLY buff the platter surfaces with the #4/0 steel wool. This will remove any existing data, level out any surface defects, and help to redistribute the magnetic media and fill in those pesky "bad sectors" that most drives have.
Reassemble the platter stack, and using a .015" feeler gauge, bend the read/write heads back to the platter surface, using the feeler gauge to set the gap. This is slightly higher gap than the factory uses, but it reduces the chance of head collisions with any flotsam you neglected to remove.
Give the heads and platters a good shot of WD-40 and reassemble the unit. If your drive has a filter, replace it with a clean section of gauze pad.
All that's left is to low level and DOS format the drive, and you're back in business. I haven't tried this myself, but my friend's wife's sister-in-law's husband knows a technician that does it all the time....
[All jokes are believed to be in the public domain. If you feel one of these belongs to you, please let us know the details and we will either remove the material or provide a link at your request.]
Unless otherwise noted, all photos and text is Copyright © Richard G Lowe, Jr.