Valance? Is it necessary?

I got in a wreck and have to replace the front bumper and lower valance on a 97 4Runner. I don't have a lot of money to fix my car so I'm wondering if I can do with out a lower valance. The guy at the repair shop told me that it would screw up the cooling system because of airflow or some shit like that. I'm just checkin to see if he's throwing me for a ride.