Having done your own research, you probably know of hitches available. I think BMW has a class 3 for the X5. The only way to get a prewired pkg, is to have it factory installed. If you are good with automotive wiring, you can add your own.
Keep your trailer purchase sized to SUV capability. While it appears you can tow about 6K, that may not mean a high walled TT. Your SUV shows just under 1K lbs of payload, so another consideration is tongue wt of TT.
Good luck with your new experience!
Jerry