If I recall correctly you can create custom fields in CS and also make them required fields (in addition to the area of expertise), so that an instruction such as "Please search by zip code, city and/or state" above the form would get you the intended user list.
Yes, you create custom fields in CB. Most of your questions are in regards to basic core CB which is entirely free and I highly suggest you simply give it a try. Even our demo site provides full access to frontend and backend allowing you to tinker with it however you like.
demo.cbdemosites.com/
You can also download our CB Primer Book below which has a lot of great information regarding core CB features.
www.joomlapolis.com/downloads/documents