Newbie help - 1 tenant wants out, found replacement

[Denise B.]

I'm a new landlord...just settled on my duplex on 7/21. In one unit, I have 3 tenants in a roommate situation. All 3 names are on the lease which clearly states no subletting and the lease runs until 1/2011. One of the tenants needs to move out and has found a replacement. I'll run the credit check and standard application process for the potential replacement. How do I handle the lease? Should I ask the 2 remaining tenants and the new one to sign a new lease together, terminating the old one? Or do I just swap names on the original lease and have everyone initial it? Other ideas?
Thanks in advance - you all are a great source of info!