Just curious did you check out the link I left you for Hughes net forum.
There are 2 different plans from what I can see and if you want to run LimeWire or any other P2P app then you will have to have the Static IP plan where they give you a IP Address. The Dynamic plan which is what I believe you have
Will Not Allow You To Set Up A Port any way I would advise you to go to the link below and see if the can help you.
http://www.dslreports.com/forum/sat