Pete and Rrambach- welcome to the board... and another vote for both Hargrove and Feathercraft. They're both great shops. If you wait until you get to St Louis take your rod and reel in they should be able to rig everything up for you, and will either recommend or let you try out different lines. There will be a lot of opportunity for chasing trout in missouri: Trout Fishing in Missouri
But you can also get started sooner- your rod is a great outfit for chasing panfish and small bass too. In fact, if you’re anywhere near Jackson MS, I’d recommend you check out these guys: Magnolia Fly Fishers
They’ll help you get sorted out with casting, try out some different lines with your rod, rigging, techniques and you’ll meet a few new fishing buddies for trips to local waters.
As far as lines go, you have a ton of choices, but as others have said, you'll want a weight forward, 5 weight floating line. I would look for one from Scientific Anglers (SA) or Rio. Ideally you should get a chance to cast a few to see which ones work best with your rod and casting stroke, but as a beginner, you may want to consider one that is slightly "overweight" 5 weight wf-f like a SA GPX or Rio Grand. Getting a decent line will be a big help with your casting. The MS fly fishing club might be a big help here-- a lot of clubs have casting clinics- either formal or informal, and getting a chance to try before you buy would be the best way to go.
As far as Jackson Hole---- you'll have a blast! There will be a lot to digest as you get into it, lingo, techniques etc, so keep asking questions. Instead of doing a data dump on Jackson Hole (there's a ton of info out there) and I'm sure you'll get a ton of info form folks on the board, you might want to google "fly fishing 101" or pick up an intro book to fly fishing like:
Amazon.com: The L.L. Bean Ultimate Book of Fly Fishing (L. L. Bean): Macauley Lord, Dick Talleur, Dave Whitlock: Books
and browse through some of the posts and FAQ's on this forum.
But just to whet your appetite, here's a brief taste of some of the fishing out there, with recommendations for flies, some techniques, and a snapshot of different rivers:
Fly Fishing In Jackson Hole, Wyoming -- An Area Overview
Keep asking questions here, you'll get a ton of advice and help from folks. And welcome aboard!