Welcome Paul,
Gun looks pretty good - nice beech grips. Not easy to find nice 1917 Lugers, most were used & abused a lot during the war. Judging from the limited pictures, your gun looks to me like it probably has a lot more than 90% finish - at least 95% or more if the grip straps and underside are as nice as the rest of it.
Don't know what to do for it? Learn how to take it apart and gently clean and oil it like you would any other gun - with Hoppes, CLR, gun oil, etc. Just don't overdo it! In my experience, the only thing that will really hurt a rust blued finish is strong abrasive or acid - including vinegar, lemon juice, pickle juice, and blood - so don't leave it on the table while you're eating! (LOL) The strawed (golden) finish on small parts is pretty thin - clean & oil it but don't try to polish it up, or you will end up removing it.
Be real careful if you take the left grip panel off. If you chip it, save the piece so it can be glued back on (happens a lot).
Here is a link for you to read and hopefully avoid the mistakes I made cleaning my first Luger:
http://luger.gunboards.com/showthrea...ow-to-clean-it
another one:
http://luger.gunboards.com/showthrea...light=cleaning
- Geo