According to this wiki page, USB (at least for 1.1) is doable on my board, but I can't make sense of the two pictures and the accompanied instructions attached in that page.

Is there a place I could find more detailed/clear instructions on how to do this? Also, from those who have attempted this or have it installed and functioning, does it affect the stability/performance of the device? Are there any pitfalls I should be aware of before attempting this?

you solder your D+ wire to R185 and your D- wire to R183 (in both cases to the side facing to the middle of the board. then solder a wire to gnd (there are plenty of points) and connect a 7805 (or better some step-down converter) to the power jack and basically you've got everything you need for usb (like described in the wiki).

Thanks MSB, a few more queries: what is a "7805" and where do I get this? When you say "power jack", do you mean on the USB itself or somewhere else?

As you've probably gathered by now, I am a n00b, not an electronics engineer, though I've done a bit of soldering in my time on various electronic devices, but nothing complex.

Last query - I take it I could only use USB 1.1, but not 2.0 and if that is so, are there any side effects - is the board working as expected once I put the USB in place (provided I do it correctly, of course)? Many thanks!