Seeking help with Google Analytics

Not sure if there is an answer for this but if there is, I know you guys will have it.

I have been very pleased with Google Analytics. Not understanding someone's marketing suggestion, I did something that brought my stats up for one day - not high enough to make any huge difference in SEO, I'm guessing - but enough to completely screw up my stats.

I wish I understood what this going to do or there was a way to undo it. That one day spike is throwing off absolutely everything. Average time went from 7+ minutes to 1, and I can't see how many users are going on there a day now, because I can only guess that it's somewhere between 0 and 250, due to the stat bar going above 1000 now. It also messed up the countries - I was enjoying watching real readers showing up all over the world and now I have no idea.

I'm assuming there's now way to delete the one day - is there a stats plugin that will show me week to week stats, or daily stats, so at least I can still have an idea? Or if I deactivate GA and start over will it start tracking from the day I do that or go back to the beginning of the site?

Please help! Thank you.