You seem pretty set on this, but it will prove to be much more difficult than you anticipate. Yes, the LCD definitely uses RGB, but basically the screen works at ridiculous refresh rates, 15kHz horizontal and 30Hz vertical (interlaced). Not only that, but it uses a composite sync instead of individual horizontal and vertical sync lines.
Check out these threads for more info:
99% sure i solved the dvd mystery
VGA to RGB+CSync
antichristpm seemed to be the expert on this and while it was long before my time here, it looks like he put in a lot of work trying to solve this, not wanting to buy the avelectronics switcher. One of his last posts before selling his 8 was him selling his avelectronics video switcher
If you're not using that unit you must make sure your AV switcher will do the parameters and resolutions specified above and in those threads.
On another note, I have been doing much with the factory nav hood and it looks to me as if the tuner equipped RX-8's had a separate input for the tuner. It looks to be composite since it is one wire (and presumably a shield ground). So you're in England with the PAL standard and your TV tuner will output at 50Hz. Oh, but you have an RX-8 from Japan, which is on NTSC-J @ 60Hz. Now, you might have 30Hz or you might find 60Hz, I have no idea if the composite is or can be converted. Either way neither match up with your 50Hz TV tuner, although if it were 60Hz you could get a PAL to NTSC converter and use that.
You said you were looking for pictures, have you seen this thread?
OEM Navigation Hood Retrofit for Carputer Application
The second photo shows the connectors where everything that plugs into the LCD goes. Check out my posts #30 and #41 for the pinouts.
And USB? I don't know where you got that but there's no USB anyhwere.
If you're somehow referring to the steering wheel controls they work on a single input line that detects what button is pressed by a varying resistance that is different for each button.
Here's the avelectronics product which looks to be the only out of the box solution to get video and audio to the system:
I have no idea if it handles PAL.
Besides, for that price, you may as well build a car computer