Someone is sending spam from my yahoo... if I delete contacts list will that stop?

Change your pword. ASAP! It really has nothing to do with your contacts list. What you did was receive spam, and when you opened it, not knowing it was spam, it sent your correct email address to the spammer, which was what he wanted in the first place. If changing the pword doesn't stop it, you may end up having to close the account. But change the pword now!