How hard was it to get firmware/flash it in the first place? I assume the driver updates are easy to get but the actual flashing tools always scare me enough to never try stuff like that myself.

I found the firmware in a big FTP index on hp.com (Samsung's printer division was bought by HP).

The actual flashing is normally done by a special print job which has commands to flash each of the ~7 different firmwares onto the right internal components. Yes, that means anyone with access to print on the printer can update the firmware to do absolutely anything...

But, if you're doing firmware hacking and screw it up, the software won't boot sufficiently to be able to be reflashed with that method, so you'll also want to pull the hardware apart so you can get a dump of the flash chip to restore when you mess up.

The hardest bit is not patching the code, but figuring out how the crc's, checksums, and memory layouts work. Get that wrong, and it either won't flash or won't boot.