pjman, you can do it; we can help. (No, I do not have shares in Home Depot). Your best bet is to extend the patio first. You can then cut the irrigation line outside of the extension and route it around the perimeter. You can place heads as and where needed as you go.

I would extend the patio first ONLY if you expect a cement truck or other heavy equipment to be driving around near your sprinkler heads. Otherwise, move the heads first. There should be a connector piece to connect the old piece of tubing to a new one, then run the new tubing to where you want the sprinkler head.