|Asumming you have ADSL broadband and not cable internet(If you have cable you will need a cable router) then yes you fit the RJ-11 phone cable to the WAN port on the router and the other end to the face-plate(or filter) on the wall. The laptops will then auto detect the router. Pretty much.|
Repeaters costs about $30-60 but DON'T rush into buying one before you get more advice. See how the wireless router works first.
The N-router should work with the G-adapter, no 100% promises on that though, it will depend on the router ,best check the features first, or google "backward compatble" with the model number. Most routers are backward compatable but not all may be.
As for speed you won't see any speed increase using an N-router and G-adapter you may see an increase in range though although i am no expert on that.