Location/nearby advance search widget

First off let me state that I am a complete noob and know next to nothing about code. I am hoping to just find a plug-in for this…

I am starting a classifieds ad site and would like to give my customers a way to search for ads on my site that are near typed in zip code. This would be useful when looking to buy a used car and the shopper would like to see what is available within a mile radius.

I know that many sites do this but can not seem to find a plugin that will allow me to set up a zip code fill-in and allow the customers to choose a range (more like circle (PI) of distance from the filled-in zip.

Example (sorry so rough and not in html):
—-SEARCH NEARBY—
Zip = 19466
___0-50 miles
___50-100 miles
___100-200 miles

I am using classipress from app themes. Any ideas anyone. Please remember that I am not familiar with code (sorry).