Yes, do call ahead, and be prepared to give your full food order when you call. The order acts as your reservation. Without the order there is no reservation. IIRC, the early part of this evening is pretty fully booked, but you might be able to get a table later in the evening, say 7:30-8:00.
EDIT: WTTW Prime just ran Burt's "Check Please" episode again this weekend, resulting in even heavier than normal bookings.
Hope you enjoy yourself@
Buddy