I think all centrino's have a built in NIC card ? If not the PCMCIA cards aren't all that expensive
What you need then is a wireless ADSL router and just plug it in in place of the standard BT box. That's what I did. A couple of minutes easy peasy config with the network wizard and I was wireless.
I got a Belkin router from PC World. Inexpensive and does everything I want it to.