It won't be the opening alone that will alert them it's seeing the wrong part (ac Vs n WiFi board).
If you can I would return the board as most people can't leverage the added speed. Remember it's the slowest part of the pathway that limits the entire pathway. Think pipes with water you have a 4" pipe connected into a 2" pipe the quantity of water the 4" pipe will get is 2" worth not 4".
Unless you have a good local file server (media server) with a RAID'ed drive set directly connected to a good ac WiFi to Gig Ethernet bridge the limit will be the limit of the HD you have on the serving system (review the HD's spec). Even that is not quite what you'll see as the files are not contiguous on the drive (i.e. frag'ed).
If you plan to access the Internet the limit of the carrier (and their equipment) and the other competing users on the other carriers to the web site will also limit you (let alone the limits the web site sets for a signal session to its resources).
Most of us just don't have wicked fast local servers or high speed symmetric links to the internet to leverage the higher throughput yet.
The last shoe to fall here: The first generation of the ac products are not bonding streams per a given node (2 or 3). So you really don't get the claimed throughput of 1Gig bit the ac standard offers yet. In the coming months newer products will offer this.
Bottom line here: Wait