Add geo code search feature

Hello, I have a client who wants to use the directory plugin from WPMU on her website--she wants to add a search feature that displays directory listings by nearest zip code. I found a tutorial that shows you exactly how to achieve that but it's just beyond my scope of knowledge and I don't want to break my head or my budget trying to figure this one out. The site is built on wordpress and is using wpmu's directory plugin. I also found this plugin which I can show the developer that I choose: http://codecanyon.net/item/advanced-store-locator-for-wordpress/full_screen_preview/238166 so you can get an idea of what we'er looking for. Please bid away! The project will be done in 2 weeks max! Thanks!

Atlante