You can find a field guide to Fresh Water Invertebrates of North America at the big book sellers like Barns & Noble. If they don't have one check Amazon. The best source would be to check with local universities who offer courses in Fisheries biology or geohydrology, the geology major has a class curriculum in watershed management. This is a really good study for anyone interested in stream management. The college book store will have the text books and the professor's can tell you which books to acquire.
Hope that helps,
PS. I had an after thought; back in the eighties I took a three day course at Dingmans Ferry (Close to you?) at the (PEEC) I believe that was the place. It was the Pocono Environmental Education Center at Dingmans Ferry. They offer this course or at least they did back before the wheel. A call up there might put you on the right track too.
Here's their link; http://www.peec.org/