The stock and pistol grip both look like replacements, I think; the rest looks like it might be original. The stock definitely looks like
oak.
The pistol grip might be oak as well, although it's a bit hard to tell... but that seems likely, assuming they were replaced at the same time. The fore grip is not oak -- looks like birch, or possibly beech...?
Unfortunately, it's going to be really hard to make it all match -- you might be able to match the color with a fairly dark staining protocol (alcohol- or water based dye to get the base color, followed by an oil stain to tone it -- then maybe a toned varnish to hide the grain...), but the grain of oak is so distinctive that it's hard to disguise. (And who uses oak for gun stocks anyway...? Wow.)
I hope you're getting a really good deal on this, Greyson... If you are, I'd think about replacing the wood furniture altogether -- I think you can pick up a set of original AK furniture, wood or laminate, fairly inexpensively, given how many people want synthetics these days. If you're going to put in the kind of work that a good refinishing job involves, you may be better off doing it to an original set...
If you're not getting a really good price on this, I'd look around some more. Prices are starting to come down, supplies seem to be up a bit, I think.
Just my thoughts...
And don't be embarrassed -- asking questions is good, so are AKs.