Ohhh, but you've made the right start. Making userbars is exactly how I got into making templates. ;D You'll get there, once you learn the specifics. If I can offer any advice or tips, just let me know!
Well, the best way that I learned about templates was downloading some from my friends who make them and taking a look at the different sizes for things and also the codes that they used to make certain looks. Being a good designer isn't only about the artwork....it's also about the codes that make the artwork.....well........work. ;D I found a bunch of codes that give me the general look that I want to go with and for the most part I don't deviate from them (though I do like to branch out when I find newer...more better codes).
As for sizes of things...maybe I should post a "guideline" for what each set of graphics usually runs, just to give people who are interested in making their own look an idea of where to start.