Tom,
There is no easy way back.
Requires at least using a system restore point; more reliable would be an entire server restore. Also keep in mind that if you use the new version in production, you will have to Crash-Back. All data that you entered will be lost and have to be re-entered by hand.
If you don't do billing in AC, you can ignore the payer prompt. You will need to run the tuner.
