Theorically yes, if you know C++ you can program in C too.
But in practice I think that who programs in C++ uses all the ++ part of the language and when he returns on C he could have difficulties.
While about the guide, naturally most depends by your language (personally I used the Tricky C guide and another older one written in italian) but if english is your native language there are no problems.
I have inserted the keyword c guide on google and there are some interesting results.
When you will understand the basis of C (main, include, the general structure of a program and so on) you could just keep only the following which is a reference guide, quick and useful informations without boring words:
http://www.acm.uiuc.edu/webmonkeys/book/c_guide/