I've done the software mod and it was quite easy. It involves following simple instructions to create a bootable USB stick, then using that to modify the TiVo HDD automatically (with it plugged into your PC of course).
Tool wise you need T10 Torx driver, PC, or laptop with USB-SATA adaptor, USB stick.
The hard part was realising that I needed to press F8 to choose to boot from USB (not in BIOS settings!).
TiVo works just the same as before, but with an extra 'backdoors' menu enabled. When the NZ guide data is loaded onto the community server it will just be a matter of going into that menu and changing the 'dial code' from 000 to 140 using your TiVo remote. Note that by default it is set to 140 so to use the official server for the next two weeks you need to set it to 000.
Also I have bought a whole lot more PROM chips and have plenty of sockets too, for those that wish to do the hardware mod themselves.