Can I upgrade the airport card in my mid 2010 iMac?

I downloaded mountain lion for airplay mirroring. Then i realized you need a mid 2011 or newer mac in order for airplay mirroring to work (wtf?). Spoke with a dude at apple and he told me that it is a hardware issue, in that the older iMacs do not have the wifi card (hardware) necessary to use airplay. So my only other option here is to see if I can upgrade the card to a newer one. Can somebody please help me answer this so i don't have to go buy a card just to find out.