SDL is all function calls; I write code in C and can use the basic functionality pretty easily. You shouldn't have any trouble based on what you're describing. Variables and functions are the most you'll need to use the library.
If nothing else, just write a few simple programs initializing the SDL lib, detecting keystate changes, displaying and loading an image, etc. My attitude with things computer-related is: "just do it", instead of worrying about knowing a finite set of material beforehand. If you lack the requisite knowledge you'll know pretty quickly, and you can get sidetracked learning every detail about every "prerequisite".