the lower willamette is closed until January. If you want to go before then you will have to fish above the falls. As far as gear I would use a rod rated for 30# or greater with 30# line or heavier. A heavy salmon rod will work. You can only use one single barbless hook. I use 80-120# dacron for leader and 5/0 hooks. put a sinker slider on your mainline, a plastic bead, then a barrel swivel. Then attach your leader to the barrel swivel. The length of leader will be determined by the bait you are using longer for squid and smelt and shorter for sandshrimp and rollmop. For squid and smelt you will put hook though head and half hich up to tail, when using sandshrimp or rollmop you will use bungee thread to keep it on the hook. For most spots you should only need 8-10oz some spots maybe 16oz. I usually always start with squid for bait on the willamette, followed by sandshrimp and worms and smelt. I even got a keeper once on just a big gob of nightcrawlers.
you have to wait for the fish to suck it in before setting the hook. be carefull when picking up rod when you are getting a bite if they feel you they will drop the bait.