If by blue poly you are referring to cts there is a specific type of fitting for it. Sleeving the full run is fine, we usually only run a sleeve thru the foundation sealed with foam. Just inside the foundation you'll want a ball valve for a main shutoff. At the valve you can change over to pex. I would avoid brass fittings underground as I have very little faith in the quality of any brass or copper fittings anymore. If your panel ground was bonded thru the original copper line you need to establish a new ground. Our inspector requires two rods ten feet apart.
