Mk1 estate - rear speakers / wiring

Well, 'new' 05 Fabia estate 1.4 TDi continues to impress.  Driving 200 miles on motorway, slowly behind artics and coasting downhill, it claimed 92mpg :)

I'm taking the interior apart prior to fitting some roof rails I got off a breaker, and it strikes me that now might be a good time to fit rear speakers (Classic model - no interior gizmos) to help my kids pass the time as we tour the nation at 57mph.  

My stereo has a front-rear fade option, but there are no rear speakers and nothing apparent in the existing loom for them.  So the questions:

*  Can anyone point me to a thread / page / whatever showing how to get the radio out of the dash, and showing me the pin-outs for the speaker connections?

* Does anyone know how fancy the bog-standard audio amp is - will it cope with one wire (hot) to the speakers and a return via some convenient bit of bare metal bodywork, or is it a fancier thing which needs a separate return dedicated to each channel (meaning I need to run 2 wires to each speaker).

cheers

Mark