Yeah, a 5 wt will do it. The downfall is putting enough pressure on the fish, and thus landing them quickly. I concur with others about using what you got to give it a shot before spending the money. If you find you enjoy it, and are gonna make a lot of trips, THEN buy the proper outfit.
1. I'd say a 7 wt is perfect. 8's a little much, 6 is still a little light, but either would be ok.
2. Longer is better. Streams are generally WIDE open, so not much concern about casting in tight places. The fish are extremely drag shy, so the extra length helps keep line off of the water and get a better drift. 10 or 10 1/2 footers are ideal.
3. A soft tip helps protect tippets from fish that WILL break them.
4. Flouro is generally recommended due to abrasion resistance, as teeth are sharp. However, there's no stretch, which is bad for tippet protection. I generally build mono butts and tapers with flouro tippets.
5. Unlike regular trout fishing, the reel is much more than a place to store line. Smooth drags, with stopping power, are a big advantage. As is a large arbor that allows you to pick up line quickly should a fish run at you (you don't want slack line!).
Other than the equipment above, I'd tell you steelhead fishing is all about TIMING. Fishing the right stream at the right time. Fresh and active fish hit, and old fish are tough. In the right seasons, a fresh run comes in every time the water comes up. So being there as it becomes fishable is the key to success. Every stream becomes fishable in a different time period after a rain event. So wait for rain, go up in the days afterwards, and know which streams are still too high, which are already too low, and which are "just right". Stay away from the mouths, where the crowds are nuts. Be willing to walk and explore. And be willing to fish water that's too deep or fast to see the fish. It's easy to set up on a slow pool where 50 steelhead are visible on the bottom, but those aren't likely to be the active fish.