~Extra NIC for notebook~

Hi, i have a notebook (Fujitsu) that already built in with a modem, LAN & WLAN. I would like to know can i able to add 1 more network card in my laptop? is the only option are plug to my PC card slot? cause i would like to set a NAT in my laptop. any suggestion to how i set NAT in my notebook? any recommend stable network card? can i use the different brand of NIC from my original card? and can i add an antenna for my wireless card? cause i would like my receive connection for wireless become stronger~! is that possible?? or any others hardware can help to for that? thankz in advance.