My apologies, I am sure that this question has been asked many times before. I am looking to upgrade my stereo in my 2017 corsavan. What I have fitted at the moment is the standard head unit however I want to upgrade to a touchscreen unit but am unsure as to what I need I see that there are sat nav units and others and am confused as to what I need, I also believe that I may need a wiring harness and replacement fascia. I have looked on eBay but there is so many different units to choose from. Any help or advice would be very much appreciated.