Ford Iveco 75E15 truck Radio Install

Where to begin?? I have a Ford Iveco 75E15 truck/horsebox that I want to install a radio/casette. Only wires left in the cab - no speakers - and presumably wired for what the previous owners took out. I have a ford radio out of my mondeo that i know works perfectly. At the local auction I bought a job lot of a Roadstar radio/cassette and cd changer and four speakers (I was after the speakers).
My questions - how can I test the Roadstar to see if it works? And is the wiring simply red positive, black ground and another red positive for the always on wire. Then connect the speakers.
any help most gratefully received.

although I am not familar with that exact setup. Rule of thumb follows that Red is Ignition switched +, Black is - and Yellow is constant +. However if there is only 2 red wires one should be constant wile the other switched and black to ground. This realy only applies to digital display radios as the constant keeps the clock and radio stations preset. Some REALLY old models only have 1 power wire and use chasis ground and have only 1 wire pr/speaker using comon ground. you can test the radios power wires by using a Digital Multimeter with a continuity testor hold one probe to the chassis of the radio and the other to a wire. if you get a tone then the wire is ground.

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Many thanks,
Hoever it looks like there is no power going to the wires anyway so looks a job for a pro!