Answers:
One of the easiest ways would be to extend the shipping/info model with your own extension, add a method to load it from tracking number without the hash. You can also look at Mage_Shipping_Helper_Data::decodeTrackingHash()
and see how to build the hash yourself.
I believe the intent behind the hash is to stop people from fishing for shipping info on orders/shippments that are not related to them.