Can the Airport Extreme work as a modem+router?

[superspiffy]

Right now I have a complicated setup at home. Since my Yahoo DSL modem broke down, I had to buy an Actiontec DSL Wireless Gateway to replace it. I guess this doubles as a modem and a wireless router. However my MBP can't link wirelessly to it despite having tried all forms of security including no security. So I connected an old wireless Belkin 802.11b router to the Actiontec gateway for my MBP as a workaround. I don't like this setup and my internet is slow. I have problems sending mail and logging to the Apple website. My question is if I buy the new Airport Extreme, can that take the place of the Actiontec gateway and work as a modem+router?

Edit: Also, can I hookup an external hdd to the Airport and have be accessible over the internet?

[mrbrown]

Right now I have a complicated setup at home. Since my Yahoo DSL modem broke down, I had to buy an Actiontec DSL Wireless Gateway to replace it. I guess this doubles as a modem and a wireless router. However my MBP can't link wirelessly to it despite having tried all forms of security including no security. So I connected an old wireless Belkin 802.11b router to the Actiontec gateway for my MBP as a workaround. I don't like this setup and my internet is slow. I have problems sending mail and logging to the Apple website. My question is if I buy the new Airport Extreme, can that take the place of the Actiontec gateway and work as a modem+router?

There's no modem in the Airport Extreme. It is just a router and wireless gateway.

Edit: Also, can I hookup an external hdd to the Airport and have be accessible over the internet?

No. It will be accessible to the computers on the LAN, but that is it.