Hypothetical Questions

So, let's say I have a "friend" with a Mac laptop. Silvery grey in color, purchased during the late-summer of 2001 for a mind-boggling large amount of money. I think the term "Titanium G4" has been thrown about in terms of this machine. Let's also say that this friend doesn't have the time to keep up on all the minutia of owning a computer in modern times. Is there some sort of card that can be purchased for this machine that will allow it to make use of the free wireless internet that appears to be available in more and more places? If so, how would one identify which card to purchase? Is it considered a faux pas to bring a laptop to the computer store and ask for "whatever I need to make this do that wireless internet thing"?