can i combine my internet and file sharing with one wireless device?

hi guys

i currently have two pcs networked together. i one of the pcs has adsl. the other used to have a modem connection but since i changed over two adsl, i no longer use dial up, and thus, that pc no longer connects to the net. I have just bought a new pc with wireless connection. only problem is that nothing else is wireless... so im looking into going that way.

my adsl modem is currently from dlink.com.au and is a DSL 302g.

is it possible to have my three pcs connected on a wireless network so that i can transfer files and also use the internet on any machine. or can i still physcally connect the two older pcs so that they share the net and files of a LAN and also have the device broadcast a wireless signal that can also provide internet and file transfer. The latter would save me some money from not buying a wireless card.... i dont knonw how expensive they are anyway.

thanks for your advice.

chris