Problem With The Colour Gps Stereo

[exon16m]

I am trying to install a sub in the rear but no one will touch the GPS unit (including toyota and halfords) could some one please tell me:

1) If the unit has a pre out?

2) How to access the rear of the unit easily (full instructions would help)

3) Is the job very complicated and risky

4) does any one know of anyone with expereance who will install the wires

very grateful

thank-you Matt