Well, the Luger is worth between $350 and $20,000, and its holster is worth $5 to $500.
I'm not being sarcastic -- there are so many variations to Lugers that it's hard to pin down value without a lot more info, and preferably sharp photos.
It's PROBABLY not a really valuable one, because the Frenzite grips are definitely aftermarket -- they were made well after the war, in the 1950s and '60s. It's also hard to say whether it's all matching without completely field-stripping the gun -- even the firing pin is serial-numbered, and if that number doesn't match, collectors won't touch the Luger.
Even with the aftermarket grips, it's at least a shooter -- which range from $350 to $500 -- and if the bluing is original and all the metal parts indeed match, it could bring up to $750 or so. If the widow lucked out and it's one of the many extremely rare variations, it could be worth much more, even wwith Franzite grips.
Luger holsters are equally collectible, but a nice aftermarket one from a common maker might be worth only $5; a nice but common original goes for $100-$200; and a rare original might fetch $500.
For a lot more detail, check the experts over at lugerforum.com -- nice and knowledgable group of guys.
HTH.