CrossRoads:
liudr,
USPS does have customs forms, with address book. My wife uses that feature a lot for my mailings.
Fills out forms, pre-pays, can even arrange for at-home pickup. If dropped at the actual Post Office, all they have to do is scan the barcode.
Is it priority or international first class? I'm shipping first class and can't find electronic way to fill forms or pay.