Rear shades were an option. There are several options for units with apple play. I have a Sicane unit. Unfortunately it was one generation before apple play. I think the Avin and Dynavin units are more popular. There are several threads about installation here that might help, I have DSP so install wasn't much fun. IMO Quicksilver is the resident go to for which unit to buy.

When towing an empty trailer it helps if you add some weight to front of trailer to get some tongue weight and reduce amount of trailer bounce. The trailer is also less likely to start whipping around.

I agree with those suggesting you keep your X5 for the time being. I subscribe to the devil you know is better than the devil you don't know. If you already had something that you go to sleep thinking about I probably would move forward, however, still keeping the X5 protects you from buyers remorse and you will find out which one sits and which one you drive. You are almost done with what you want to do to the X5, it is low miles and is fine for towing.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas