How would I go about plotting a single pixel or a line in SDL without using a rect...is it even possible? Also is there anyway to use GFXLib commands inside of an SDL app window?
If you use plain SDL, it provides no means to draw pixels nor lines. You just have the framebuffer to play with, blitters and filled rects; you have to code your own pixel and line plotter routines... there are examples about this on the SDL site, under the docs section. There are extension libs out there though that provide you with gfx primitives for SDL, without the need for you to reinvent the wheel, you may want to check out the libraries section on the SDL site.
As for gfxlib, if you use SDL forget about using gfxlib routines, it will just not work.