Tools and Parts: three hands, medium-shafted Philips-head screwdriver, film canisters.
Before you proceed, make sure that the Lisa is plugged in and that (if the Widget is functional enough) you have booted the Lisa from the hard disk at least once after plugging it in last! The Lisa stores critical system parameters (time/date, device info) in two places: the PRAM and the boot blocks of the boot disk. If the Lisa is unplugged, the parameters in the RAM are lost and must be restored into RAM from the boot disk. Installing a replacement Widget with no parameters in RAM may cause incorrect information to be "restored" into parameter RAM. Incorrect parameter info causes many system problems - be careful!Step 1, Preparation: With the Lisa off, remove the front bezel by pushing up on the two tabs underneath, then pulling out. Loosen the finger screw beneath the floppy drive. Pull the entire drive assembly out of the cavity and rest it upon a clean, anti-static surface.
Step 2, Disconnect: Looking down upon the assembly from the front, remove carefully the three cables connecting the unit to the Lisa: the Widget power cable, the Widget data cable, and the floppy cable. Next, disconnect the two-lead fan cable attached to the top right of the uppermost board. Memorize how the fan wire snakes up around the Widget - you will need to know this later
Step 3, Detach: Gently lay the assembly on one side. Remove the two screws holding the Widget support plate in place in the aluminum rack and optionally place them in film canisters. Carefully turn the assembly over, taking care that the Widget does not shift. Remove the other two screws.
Step 4, Remove: Carefully set the assembly upright with a hand underneath the Widget to prevent it from shifting. Gently spread the aluminum cage, pulling the fan wire away from the Widget in order to avoid a tangle. Lift the Widget up and away from the cage and set it aside.
Step 5, Replace: Pull the fan wire taut and carefully spread the aluminum cage. Lower the new Widget into the proper position, while being careful not to tug or scrape the fan wire. Try to keep the wire from being squashed - remember how it was before you removed the old Widget.
Step 6, Cleanup: Replace the holding screws to secure the Widget in the cage. Reconnect the wires.
Step 7, End: Gently slide the cage back into the Lisa. Be very careful that the cables do not get caught on screws inside the case. Apple mentions this on the TIL, but I can't find it for the life of me! Replace the front bezel and power up the Lisa. If the Widget hasn't been used for a while, it may take a while before it actually starts to work! (or at least this is my experience)
Source: Tom Stepleton / http://web.archive.org/web/19980212223305/galena.tjs.org/~tom/service.html[LisaFAQ] > [Hardware] > [Hard Drives] (Comment on this answer)