it should be an additional card.  wireless card and LAN card do not replace each other.  you could also remove LAN card and use the onboard LAN port. Dell oem antenna [URL]
Hi, I own a Dell OptiPlex 3020 and wanted to know if there's a possibility to insert a wireless network adapter card, or if must I connect it through USB (which is less favorable to me). If it is possible, which card do you recommend (I know it should be very old card technology).
OptiPlex 3020 Network adapter card