Just to report back.  I just loaded a saved flight, then following your instructions called up my previously saved flightplans in the CDU.  Selected one and then - I think - was able to load it by pressing "execute" (?) and pressed LNAV and presto, it started following the route.  Interesting I could see the route in the left ND but not in the GPS popup or the FS map.  Anyway, I think I am making progress.  Was not able to follow really the arrive/depart and runway selection thing - I keep getting arrival info for my departure airport, but will keep experimenting.

Question:  if you wanted to change your FP mid flight is there a way to input a different destination ICAO into the CPU and fly "direct to" that different airport?