The best way would be to purchase an ethernet modem/router/wireless access point. I usr the Netgear kit and have found it first rate.
So, you will need:
PCI Ethernet Network card in PC - If you also want PC to be wireless, you will need a wireless card instead. I have heard that Netgear wireless PCI cards have trouble if you have an Athlon Chip in your PC. This does not apply to the router. (My PC is an Athlon, wireless router is Netgear)
PCMCIA wireless card for laptop (as you said)
Ethernet cable (straight through - cat5) from Modem/Router/WAP to PC so that you can configure the router. If you then go wireless to the PC, the cable will be redundant. The Router will come with one. Do not use your existing crossover cable.
You should be able to pick up a router PCMCIA card bundle from any of the big suppliers such as ebuyer click here