expiration date and change in terms

I am in sales for a local roofing company. I signed a no-compete agreement to continue working for the company. I have since become unhappy with the work environment and want to look for another job but I'm not sure how the agreement will prevent that. I have two general questions I am hoping you might be able to answer without actually seeing the contract. First, the no compete that I signed has an expiration date on it, which was on Dec 31st 2007. It is now Jan 2008, so the expiration date has been and gone now. I have not been asked to sign a new agreement, nor would I agree to. Does the expiration date mean the contract itself expired on that date, thus making it null and void until I am asked to sign a new one?? Second question, the terms of the agreement outlined my salary and benefits I was to receive for my work as a salesman. This week, the company announced to all sales personel that in 6 months (July 1st 2008), sales members will no longer get a paid salary or benefits and that instead we will be paid on a commission only basis. We have not been made to sign anything to reflect the change in the terms of our original agreement so far. Does the fact that we have been notified that the original terms will change in 6 months void the agreement in any way? Any info would be appreciated. Thank you