I have a primestar dish also, and have thought about using it for something other than a useless house ornament. The primestar dish was designed for the Ku band, I have read that they could be used up to 10ghz. Just recently I found a page at the San Bernardino Microwave Society site that mentions one of it's members designing a chapperal feed for 24ghz on the primestar dish. The url is: http://www.ham-radio.com/sbms/newsletters/1999nwsltrs/jan99.html
As far as the receiver and LNB is concerned, I doubt that they would be of much use. Hope this helps and let me know if you come up with something good.
73 de KD4ZGA Jim