How to get started modding for source sdk? Thread

Hi

I would like to get started modding a game with the source sdk. However it seems a bit complicated.

First off i need to choose what source sdk to use. I figgured the 2007 base would work. Im looking to makeing a mod that only requires HL2 installed, thats the only game I have using source engine for PC. Or would a mod only require ppl to download source sdk (which is free), ppl dont even need HL2 to play mods?

Anyway the tutorials/info i find next tell me i should run source sdk 2007 throuh steam and setup the mod... but the sdk only has a graphics test for framerate. Seems to be not working.
So i find some other information that the 2007 base is outdated.. some other info to use "source sdk" only.

Can somebody explain this?