There's already a thread about this under the guide, but as many people have stated, it's not the easiest thing for an electronics novice.
http://www.350z-uk.com/forum/viewtopic.php?f=35&t=41330&start=0
If I was to sort the trader fee, who would be interested in a pre made kit, not using all the clips, large relays and wires in the above guide, but a nice, small printed circuit board with a few wires coming off to connect to the loom. If I can get enough interest, I can bulk order which would bring the price down and could probably even fit it if you're close enough.
It obviously won't have these components on it, but would look a little like this:
This will need a bit of prototyping to get it to fit on a tiny unit, but should be easily done. So who would be interested?