H1B extension with passport expiring in Sep,2015

I am on h1b which is valid till 1st Nov,2014. My company is filing for extension. But my passport is valid till 20th Sep,2015. The extension can be filed as I still have more than 6 months valid passport. But I wanted to know the implications of this. Will visa be extended till valid passport date or it has no impact on the no of years of visa extension?
If my visa is extended and I get my passport renewed after extension, do I need to get it stamped again? What is the course of action I need to take in this case?