RENAULT KANGOO TREKKA 2003 FAULTY HORN AND FM RECEPTION

I Have a low mileage trekka 1.9 cdi the horn has stopped working and the fm reception is poor. before I investigate both problems I would like to get advice on troubleshooting and more importantly how I can access appropriate parts diagrams which will give me some schematic on how to troubleshoot and how to remove interior trim to get to where I need to for the aerial cable. I have done a search but not come up with any obvious answers

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