Not so sure on free, but, if you know c/c++ finding "conversion" info is actually harder than finding "this is a computer" level starts.
I like the 3dbuzz vtms (xna 101 vol1,2&3) which while aimed at xna spend most of the vtms showing OO and coding concepts etc in c# rather than xna persay, its just the application of what you've learnt in that sense. You can find them at www.3dbuzz.com
Other than that, decide on an app and try and write it. Sure some notation is different between c++ and c# but its very similar in a lot of ways. Of course annoyingly enough different in others.. such as converting eveything to strings with .ToString() or such but, its very easy to get on with.