That is exactly what you will get. I ride some pretty rocky mountain trails, and the stock gearing was no good. It was real hard on the machine, and me as well. I went with a 13/39 combo. It's just right for me.You could even try a 13/40 if it suited you. The lower gear combo will definitely help climbing rocks and hills. I also put on ITP Blackwaters on the back to help with traction. I even put 23 inch tires on the front, for a little more clearance. I am very happy with this set up.
There are some good sprocket companies on line. Personally, I recommend a hi tool steel one from sidewinder. A little more expensive, but they are very durable. I've used the chain lube they will try to get you to buy. It does leave a little bit of a waxy buildup. I'm not sure I'll buy it again.
Scott