Cn anyone show me a diagram of how to best plumb a corn boiler with a backup furnace and 2 zones?

Also i am adding on to my shop and wondering if there is a way to couple pex tubing together to extend it when it will be under cement.

There is a book call "Pumping Away" by Dan Holohan. A must read for setting up boiler, or in series. You can find it all over the internet. Best money I spent before starting on plumbing my boiler!

As far as the pex, check out PexSupply.com.