I have no experience with C or C++ so I am concerned about trying to learn CUDA. My recent experience has been with C# and limited to database applications. In the past I used cobol and fortran to complete some basic statistical analysis in college, but that knowledge has fled my mind.
CUDA is basically C syntax (with a bit of C++ templates) plus some special functions, so it will look somewhat familiar if you know C#. You will need to be comfortable with pointers though, so you should find a book on C to learn that.
The CUDA Documentation is very good, but you’ll have to read the Programming Manual a few times to absorb it all. Chapter 7 provides an example CUDA program with explanation.