Hi JB I'm not a fan of wire for fly fishing. I like using 80 pound test line around 6 inches, I also use straight 15 pound test line for my leader for my 7wt and 20 pound test for my 10wt. The lenght of the leader should be around 8 to 9 feet for floating line and 4 or 5 feet for sinking line. anywhere in the middle for intermidiate. Your rio 7ft is fine, just be aware that your flyline breaking point is around 20 pounds also. so put a tippet between the leader and the wire or heavy mono.
I like using the albright knot.
I also use the Alberto knot.
For tying the fly to the leader/tippet I use a Homer Rhode Knot, so the fly could pivot and have more action.
For the 8wt. you should have no problem handling the fish. once you get some experiance. Use the butt of your rod to fight the fish, and palm the reel to add drag when needed. The weight rating of the rod is more for the size of the flyline. The flyline is what carries the fly. If the fly is to heavy for the flyline it won't cast well. you will have to match the fly to the flyline. good luck