Helo ..
Just take a look to reference site, i could add these search feature that filter by selected value and other element. My name is Shelingholmes, i am Wordpress developer, 3 years experience in this field especially in Tweaking and Feature development
To do this, we need to add support content to each post ( or meta value ), so user could always get what's exactly they want from what their search in form. We also could display featured listing above of search form by inserting a shortcode ( that will be generated in plugins )
Final file will be given as Plugins, so your site is secured from fatal error PHP, and safe from any automatic upgrade..
For consideration, please take a moment to visi my profile, there are some reviews & portfolio related wordpress here.
Please let me know if you're interested, if possible, i would like to discuss further details related this project.
Thank you ^_^, and
Regards,
Shelingholmes