I am not the developer but I have been shoulder deep in the plugin over the last few days editing core files. What exactly are you trying to change?
Are you just wanting to change Labels? Or actual Fields?
As far as separating the plugin comes with certain taxonomy built in. So to display only used vehicles: https://www.YOURSITE.com/condition/used
Or to display only new vehicles: https://www.YOURSITE.com/condition/new
For manufacturer us the same system: https://www.YOURSITE.com/make/dodge (or whatever you input)
Instead of worrying about “cars for sale” vs “trucks for sale” you can just create menus to taxonomies.
https://www.YOURSITE.com/body_style/sedan
https://www.YOURSITE.com/body_style/truck
Hope that wasn’t too confusing. Good Luck!
