New JVC KD NX5000 wiring help please.

[KPM]

I have just purchase a new JVC unit which includes a sat nav,part of the wiring instructions say that I need to tap into the speed sensor and the parking brake for the video play.Can any one help me locate these wires please on a 2001 SLK 230.

Kev

[KPM]

I have been told the speed signal cable is behind the radio and is green/white and the I should wire the video wire to a permenant ground rather than the parking brake wire so it works on the move.Can anyone confirm the above and if so were do I find a permenant ground.
I would like to get this fitted so quick help would be apprieciated.

kev