pdlucky- Welcome to OFF! I have fished the Willamette in Salem, but never from Champoeg...I expect other members will be able to give you advice on that particular stretch of river. I have seen everything caught in our part of the Willamette system from Steelhead to Smallmouth Bass. I have had good luck there using spinners, spoons, and bait under a bobber. Plunking also works well, but it depends on how much algae is in the water at the given time.
Good luck, and be sure to post an after-trip report on your success.