It's easy enough to do your self.. for the amp you will need an amp wiring kit, available from Halfords, autocraze, motorworld, ebay etc. (go in and ask them they will tell you what you need) run the main power cable from the battery through the car to the amp, the earth can go to a connector behind the carpet in the boot near the rear light and you can connect the remote to the 12v socket in the boot, using crimps or something similar. Run the rca cables from the amp through to the audio out socket on the radio, you'll have to take it out to feed them up the back whilst its out you can plug in your new radio. Then just run the individual speaker cables to each speaker which you can hide behind the trim and feed through the same hole in the door that all the door wiring goes through, pull door cards off take out old speakers and connect up the new ones using your new wires.
And viola a few hours a lot of swear words and a mate pissing himself while he watches later and your all done
If you weren't so far away I'd offer to help you out for a hell of a lot less that £350, but good luck
