Installing additional packages using opkg manager

I am a newcomer to Linux and just ordered and Overo Air yesterday with Palo 43 so please excuse any naive questions I may ask.

On the Gumstix website, it says that there are many more programs that can be installed using the opkg manager. Are these programs stored in the 256 MB of on-board memory or do I need to setup a build environment on my desktop first before I can add the extra packages.

Also, I am trying to build a PMP so are there any packages that would be of interest to me? I am already happy to see that the factory installed software comes with a web browser and video player. Is there something included to manage the Wi-Fi connection?

Sorry for all these questions, but I am very excited to get my Overo and want to learn as much as possible before it gets here.

Thanks,

Gumstixdude