I'm with gunut on just using some oil. I used linseed based oil on the "light" part of the 70 -80% stock on the 1950 Mod 94 I got over the summer. My reading and research indicated 94's left the factory with a linseed oil-based finish. So I figured using linseed-based oil wouldn't hurt anything. "First, do no harm." Hippocrates.
I learned the oiling would not be a one shot fix. Just a thin, hand-rubbed coat every now and then, feathered in to the good part of the finish. It's healing up real nice. I still a few coats to go.
I don't know what the factory finish was on Model 100's. Perhaps you can find something on-line, on Amazon, or in your gun library about that. That way you would know the original look for sure.
An 80% wood pre-64 Model 100 is a nice rifle. My stock was 70 to 80%, so not that far off yours. We're talking 50+ year-old tools here. I don't think I'd take sandpaper to it at all, but I like 'em original. I've still got 80% of my hair and teeth and I'm more than happy with that.
If dressing up the your old girl makes you happy and you're not worried about collector value, go for it. If you want to hedge your bet, research a little. Maybe the oil treatment will do what you need, leave your options open and not hurt anything.
That's my long-winded 2 cents. Good luck.
