Use the previous release as an integration baseline. Either the example in the Fowler book or the example at the Xplorations site will work. Finish going through the refactoring example. This topic is large enough it can easily span two weeks. QA runs user acceptance tests to validate the user stories are complete.
Developers support integration.
Issues such as, Tracking Developer Time, Documentation and Resisting Changes Mid-Iteration. One source of information might be the Extreme Management page. Iteration Planning for the final iteration. Try to plan for enough work to match the velocity of the third iteration. Developers write programming task cards and QA begins writing user acceptance test plan for the chosen stories.