Ok, now that its not throwing errors in the cart, I'm trying to test if it works. The problem is if I select the sandbox, it says that my account # doesn't exist?! If I put it in regular mode, I can get all the way to the second screen where you confirm the charges, but once I hit confirm, it says I can't purchase from myself! So I'm not sure how to test if its working at this point.

Any ideas on why it says I don't exist in with sandbox enabled, but apparently I do exist with the regular mode. (?)