The Walther P1 is an aluminum framed, post WWII version of the German P-38. They not as collectable, or as valuable, as a P-38.
100-1000 USD
100-340
See Dieter Marschall's book Walther P1-99
Complete description of ALL markings.
100-1000 USD depending on EXACTLY what you have.
100-300 USD
50-500 USD
No such Walther. You can have a Model 1 or a LP1.
100-300 depending on condition and accessories.
About $500-$600 new. Used, $250-$450, depending on condition.
100-400 USD
$450-$550, depending on condition.
Depending on condition, around $800. And that is 9mm Kurz (German for short)