Heck Yeah..
if you can book.. I would do it.
I have my ceremony site booked already for our 9/19/09 wedding, and has been for quite a few months. But the reception site wont let me book till a year out.....
So if you can do it, by all means ..DO IT!
I think it will ellimintae tons of stress, I know it has for me in regards to the ceremony site.