If by clamshell you mean the old loo seat jobbies, i think the late ones came with the airport card, not sure, they might have gone to the normal laptop shape snow ones by then, the older ones will need one of the old PCMCIA style airport cards fitted.
The old cards go for ridiculas amounts of money for what they are, i've been looking for a cheap one for some time to complete my old ibook, but they've all been to expensive to be worth it
As to the software, that depends alot of the version of MacOS it's running, my old 300Mhz one came with 8.6, and soldiered on until 10.3.
Do as mkrishnan says, and let us know what you find