I am soooooooo tried of looking at cars!!! Since I can't find anything, my standards, and therefore my price range, keeps getting higher and higher. I want a used Celica and I'm contimplating:
Should I spring for a 2003 with 66,000 miles for $13,000, or risk it with a 2000 Celica for $6,000.
These prices aren't final and I know I can haggle them down a bit.
What do you think?

It all depends on the maintenance of the car. It could be used up at 100k if the maintenance records show late or missed maintenance. There are plenty of Celicas that have 200 k on them.

I think you should more patient. Maybe a better option might arise if you do. But if I had to choose between your two cars, I would choose 2000 celica. Though it has 100000 mi, if you give it its routine maintenance it should last. Just make sure the car doesn't act weird or make any weird noices.