Greetings Amolkakkar!
Your Samsung 850 will most definitely work by swapping it with the old one. Before you do so I suggest you create a recovery media via USB from Windows if are not planning to use another operating system. Take in mind that doing so will void your warranty unless if needed you swap your old drive back prior to shipment. There is a possible risk with activation I might add. Just make sure you have a good hardline internet connection to assure stable connection to Microsoft’s servers. You may contact ASUS support to track down your 5x5 Windows key as well. You will want to provide them with your information such as your model and serial number to pinpoint that. Good luck and happy modding!!!