The multiple category search addon is something I offer to those that request it who have purchased either the Pro Pack or Extension Pro Pack. I also installation/configuration as a service for this addon. It can be complex to configure due to the syntax required to define which categories to setup for search. If you are familiar with shortcodes, this it is not that bad. I of course provide instructions and am available to answer questions.
It is best to use this addon on a page different from directory page. Also, if you use a template which has these category filter and keyword search on by default, you would want to turn those template features off.
It also has, an optional, search by zip code radius. If enabled, you will need to setup a Google Maps API key to use with Connections.
Hope this helps!