Not my tutorial, but . . .
What perlguts goes over is the internal C structures that represent scalars, arrays, and hashes in Perl. The xs code can do some of this for you, but as soon as things get the slightest bit complicated, you'll almost certainly need to know how to interface with SVs and such.
Don't worry, though. If you know C already, adding this on isn't that hard, and it's all pretty well documented.
"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.