Wireless Networks: Connecting buildings together

[KTorak]

I need a little help here. Whats the best way to connect 2 buildings around 600 ft apart? I currently have a Linksys BEFW11S4 wireless router.

Option A:
Figure out which antena port on my router to use and plug in a Directional Antena to the building.

Option B:
Setup a Linux box with router app (I'm sure I could find one) and use a desktop card..but remove the antena and connect a directional one.

Foreseeable problems with A:
I think I'd lose my local wireless if i removed an antena and shot the signal to another building.

Foreseeable problems with B:
Aquiring a linux box and the software to use.

General probelm:
Would I need a directional antena at the other building to shoot the signal back to my house so they can communicate?

Any help is appreciated.