Read the instructions on the Snow & Ice Barrier first. It should tell you if you can use it in valleys AND if it should be installed after the felt.
For more explanation of how to roof, see Roofing Application Instructions. After this, find a roofing 'laborer' that will work w/you for a few $$$ an hour on weekends to help you with the 'tough parts'. Believe me, they're out there!