What authorized dealer would authenticate a Cartier Pasha

Dear friends;

I recently bought a Cartier Pasha seatimer from a reputable dealer on eBay. (47500 watches sold, 100 % feedback, 30 days return policy). I went to a store to try the real watch and I loved it. I received the watch today and it look great, perfect size and weight. I have 30 days to return it if I am not satisfied. I got it in an auction at $2900 (it's worth $7845). Frankly it looks and feel like the real deal. There is no flaw that the naked Eye could spot. I am humbly asking for your help and expertise to make sure this watch is real.

What is the best way to have it authenticated by an AD?
May I simply take it to Cartier and ask for Valuation for insurance purposes?
There is a Tourneau dealership not too far from my home should I take it there?

Thank you for your advises.