After I sent in the signed promissory note, I received a confirmation letter a week or so later. Once you get the confirmation, you are set until the school disburses the loan checks. Some schools do this a day or two before classes start (I think) and others do it the first week of classes.
If you are unsure or a little paranoid, call them and see what they say. I'm betting that you are good to go.
Erin