I have an older iMac with the arm attaching to the screen. It's a 700 MHz PowerPC G4. Looking to add an Airport card to it but not sure if it requires a specific type or if there are even different types. How cna I figure this out and where would be the best place to buy one affordably? Guess I may as well upgrade the RAM while I'm in there. There's only 384 in there. So if you can give me advice about that as well I would be forever appreciative.