I've got the Blitz LM kit, fitted it myself. Had to massage the back of the standard bar slightly with a 4" grinder but other than that not really much effort required.
Easiest way to find a vacuum leak is to open the bonnet and then either have someone work the accelerator or open up the throttle and listen for the hissing sound. Usually is just a cracked piece of hose.
Mine has only just hit 90000ks and is having all that stuff done. Its also having the PFC installed and tuned
I'm going for stock Nissan belts as the aftermarket ones cost a lot more and most of them make a shitload more noise than the standard ones.
The Blitz i-Colour will not show all the extra fetures unless you buy the all the sensors to go with it. I don't know why you would need all that as all the instruments on the dash have the info you need.
The shape is the same as the base/mount of the Pioneer Carozzaria DVD/GPS unit that came with my car. It is for mounting the monitor/screen in unconventional places.