My Range Rover started shaking at highway speed, where do I take it?

Last Friday I was driving back from a family trip and my Range Rover began to shake when I passed about 100 km/h. The steering wheel was vibrating a little, and I also felt it in my seat, which scared me, so I slowed down and drove the rest of the way very carefully. It is a 2015 model with around 110,000 km, and I have owned it for two years without any big problem until now. I called a few places on Saturday and got very different answers over the phone. One person said it is only wheel balancing and will cost almost nothing. Another said it could be the brake discs or a worn suspension part, and a third just told me to bring it in and he would see. So now I am stuck on one simple thing, where to fix a Range Rover in Abu Dhabi without paying for parts I do not need. Should I go to the dealer first, or is a good independent workshop enough for this kind of problem? How can I tell if a workshop really knows these cars and does not just guess? Is it a good sign if they ask to test drive the car first? Should I ask them to check the tires and balancing before anything bigger, since that is cheaper? What is a normal price for a full vibration check, and do they take that amount off if I repair the car there? Is it fair to ask for a written quote before they start any work? I also wonder if the air suspension can cause shaking like this, or if that is a different problem. How long does this kind of repair take, and do I need to leave the car for a few days? Another worry is safety. Is it okay to keep driving for short trips until I find a place, or should I stop using the car now? If you had the same shaking problem, please tell me what the real cause was and how much you paid in the end. Did the repair fix it for good? Even small tips about what to ask or what to avoid would help me a lot. Thank you for reading.