You can only get R&D mode by using the flasher, but it doesn't reflash the firmware so you won't lose any data by enabling R&D mode. The flasher tool simply sets a device attribute in flash memory. The flasher tool on Linux & Mac do a lot more than flash firmware, which is all the Windows flasher tool (Wizard) is limited to. This means you can only enable R&D mode from Linux/Mac (actually I'm not so sure about Mac, but I think you can). Use a Linux LiveCD if you don't have a Linux machine.

Alternatively, see step 2 which explains how to install the becomeroot package which makes R&D mode entirely unecessary.

As a final tip, see SSHing as default user, not root.