Screene-
Take a look at this URL. He does a great job of explaining it. It is a fiddly procedure.
http://www.webbikeworld.com/t2/valves/
I don't think it really matters which way round it is but I would orient it so the IN is on the intake side (toward the back of the bike) and the EX toward the front.
Hope that helps. Please share any tricks you discover in the process.