I have been through this type thing many many times. Nobody but nobody backs up data.
For the best shot you need not only same model CB, but same firmware version.
I just tried to save a maxtor 20GB that had two years of work on it for a friend, and made the mistake of letting him order the drive - the firmware was different.
So we had to send it back for another.
His drive only had one platter - thats the easiest.
Multiple platers means you have to mark the outside edge of the platters somehow so that they can index on motor shaft same way (synchronize to previous positions) and how they stack on spindle. (1-2-3-4, not 1-3-2-4)
You will only get one shot at it - once the drive is turned off it will not move head assemblies again. (air cushion disturbed by particles)
When first trying CB replace, you will have to carefuly lift board at 18 pin data connector so that you dont bend pins.
My friends drive (PC) had been dropped while being transported from 3rd to first floor in office building and wands were stuck past park position.
When he tried to boot, since the wands couldnt move, he then fried the servo voice coil.
Before knowing this I tried the freezer trick, which did free the wand assembly (green activity light no longer stayed on all the time), but it could not seek properly.
Frozen motor bearing or burnt voice coil or mag pickup head broken off means no recovery without disassembly possible.
He then sent it out and paid $2200 and got his data.