I agree with all who suggested getting to know it on a lake. The thing I would add is to hire a guide who gives sled lessons. I did this when I bought mine a couple of years ago, it was the best $150 I have spent. The guide that I used was Dave Mullins, we ran the Skykomish. Learned more in a day than I would have learned in a year. As for a river to run the Cowlitz from Blue Creek to the Mission Bar is at a good level to learn on right now, just have to dodge the 40 or 50 boats that will be out there with ya. Have fun with the new sled!!!!
Good luck and tight lines, Jeff