You may not want to waste an ounce of Cascade as a bittering hop. It is hard to get now, so you may want to save it as an aroma/flavor addition for a pale ale or IPA.
Just sub the extract for the munich---get munich extract if you can. You can omit the peated malt if you don't want a smoked porter. This is one of my all-time favorite beers, homebrew or otherwise. I love, love, love it.