I feel your pain. The 555 timer is how I started out and trust me, it was crazy trying to find info on its operation, but Google is most definitely a valuable resource (as is the library!). Anyways, I'll give you a quick rundown...
Since all you need is a pulsed output, I'll show you what you may have already learned - the astable mode.
http://www.box.net/shared/ahohc5moxa
Above is a layout on the right, and the schematic on the left. Since you bought it from Radio Shack, it should have the pin layout on the box (got mine from radio shack too, lol)
Anyways, the resistors and capacitor are the things that pretty much what set the Time High and Time Low. That basically means, the on/off time. Now, I'm not sure what the specs are for your project/application, so here is a formula you can use to calculate the frequency of pulses.
TimeHigh(on)=0.693C1(R1+R2)
TimeLow(off)=0.693C1R2
Frequency(in Hz)=1/(0.693C1(R1+2R2))
Here are some tips, though, so your math comes out right...in these equations, you want to put the resistors (R) in ohms, and the capacitor (C) in farads. Example, if you're using two 470 ohm resistors and a 4.7uF capacitor, it would be like this...
Frequency=1/(0.693*.0000047(470+940))=217.75Hz
Resistors are easy, but capacitors, well, they end up having a lot of zeros. You will see most capacitors with a value of something uF. 1 farad is 1,000,000uF. A lot of zeros.
Anyways, I hope this helped you a little bit. The math can get a little messy but in the end, the 555 timer is a lot of fun. Good luck!
