On top of the other suggestions I'd like to add spend LOTS of time reading this forum. Particularly this tab to learn about Sonar, the Techniques tab to pick up general knowledge and the Songs forum so you can hear what kind of results others are getting and some insight into how they did it.
A lot of it won't make sense at first but as you go through the tuts, manual, vids and whatever other resources you can get your hands on you'll start to get an idea of what's up and people are constantly posting links to other learning resources.
I came here two years ago and had absolutely NO idea what the heck was going on. Now I can use almost every major function in Sonar and produce full songs from start to finish without too much trouble. They may not sound super polished yet but I'm working on that. lol
Good luck and if you get stumped ask questions. These guys are super helpful. Cheers.