My Boze came with a "leather" case, so step one was correct using a hex wrench (if you have the leather case, pay attention to how far the screws are into the leather, as it is possible to overscrew them and damage the leather). For the second step, I had to gently bend the leather case away from the back (<1 inch) and use the 10 Torx (star) socket to remove the screws, elevate the old battery out, seat the new battery, and replace all 4 screws. Am waiting for the replacement to charge and calibrate. My old battery was still working, but showed a random undercharged (yellow) battery light, so it was just a matter of time: I think the battery was 15 years old.

The hard drive may require partitioning....the first time I formatted it as Mac OS Extended (Journaled) I created a Guid partition. I don't know whether the partition is required for the drive to function, but it didn't hurt anything, once I had the correct formatting (above).

The steps I used to install Leopard on my new hard drive (PATA) are shown here: https://archive.org/details/osx-leopard-...

or here:

I started with a new hard drive and formatted it using a Vantec IDE/SATA to USB 3.0 adapter (best $20 I've spent) on a mac running High Sierra. Using disk utility, I clicked on the new drive, then "View" and then "Show all devices". I clicked on "Erase", and the option for "Apple Partition Map" appears, and Mac OS Extended (Journaled), and ran that to format the drive. Then put the drive in the computer.
I downloaded the ISO file onto my computer. Formatted the flash drive to Mac OS Extended (Journaled), and clicked on "Restore", using the iso file for the "restore from" option, and the flash drive as the destination. This is the boot drive.I put the flash drive was in the computer and booted it into Open Firmware by clicking option-command-O-F after the chime. The drive happened to be inserted in "USB1", so I typed Boot usb1/disk@1:,\\:tbxi

If "usb1" doesn't work, try "usb0"

The replacement subwoofer connector (step 4, which disconnection is required, not optional)was just a bit shorter, and just barely fit, so it was ‘iffy’ whether I’d get it to stay, but it did. Yea! No more sound distortion!!! Such an easy thing to fix!