I'd like to build a timer to activate a 12vdc fan periodically for short intervals, perhaps on for 10 minutes every interval, with an interval anywhere between an hour or 4 hours.

Considering the accuracy of the timer is not important, nor the precise voltage produced, I was hoping I could run out and grab some transistors and capacitors from radioshack and throw something together. I'm willing to use ICs if I can pick them up at radioshack, but that seems like overkill for my needs.

Thanks for your suggestions, everyone at this forum always has such useful guidance, I really appreciate you all helping out those of us who have amateur knowledge of electronics but no formal training.

 

You're not going to be able to make a 1 to 4HR timer with a few components from Radio Shack. Maybe at one time, but not now.
I would just go buy a digital wall plug-in timer switch, plug a 12v wall wart into it, and attach your fan to the wall wart. They usually have a minimum on-time of 1 minute. The motor driven ones generally have an minimum on-time of 15 minutes.

Ken