Hello,
If you use separate search from component, in menu of search you can set layout for search: advanced and default.
You can also choose Result layout.
To edit the search to which is directed to from "all vehicles list" you need via code.
default.php or list.php
location: your website/components/com_vehiclemanager/views/search_result/tmpl
What exactly do you want change?
Thanks
Taras