To give an idea on the first question, this would require using WP_Query and adding a meta_query and a tax_query.
$args = array(
'post_type' => 'cars',
'post_per_page' => 9,
'meta_query' => array(
'key' => 'brand',
'value' => $vehicle_brand
),
'tax_query' => array(
'taxonomy' => 'catetory',
'field' => 'name',
'terms' => array($vehicle_type),
'include_children' => false,
),
);