First off, don't make the mistake of thinking I really know what I'm doing...cuz I'm still learning every time I go out. That said, if you can't wait until spring and just gotta get out and start flogging some water, the south fork and (I think) the main stem of the Nooksack are open but it's pretty much catch and release. Double check the regs and take the time to learn how to properly handle and release a fish. Be nice to them, they're pretty cool.
For flies to swing, I'll recommend a pink & purple egg sucking leech, a black maribou bugger or leech, maybe a similar one in white...weighted with hourglass/dumbbell eyes..size 2 or 4. And maybe a flesh fly or an egg pattern. Throwing a weighted fly will change your casting tempo...but there's no better way to learn than trying. If you don't have a sink tip or a sinking line, you might be able to get by with a 1/16oz worm weight and a longer leader...but that'll make it that much more of a challenge to cast.
I've been throwing flies for so long that I can't really remember what it was like starting out....other than not being able to cast a dry fly no more than 10 feet or so and getting pretty frustrated. So maybe what I've suggested is too much. I dunno, you'll have to be the judge. Consider taking one of your weighted flies, cutting the pointy part off and doing some casting in the yard or a nearby park or open area. Wear a hat. A weighted fly can leave a good welt...and protect your eyes, they don't grow back
Also go get a copy of Chester Allen's Fly Fishing for Sea-Run Cutthroat. Like I wrote in my first reply, I'm going to give them a try this spring. It's a pretty good book with fly suggestions and tactics. The SRC will be after the chum and pink fry that will be heading down stream in a few months. I'm guessing the rod you have will be perfect for them. I'll be returning the library's copy soon so put it on reserve.
If you have a boat or tube, head to one of the open lakes. Like Nick suggested a woolly bugger is a good option. A month or so ago, I did all right with a darker muddler minnow on a slow strip. And don't forget your PFD, the water's pretty cold and I'm guessing drowning sucks.
Also, get signed up for the monthly newsletter from Confluence when you stop down there, it has lots of good info.
Most of all, have fun with it.