Marmot,
You change that gun in ANY way, and I will personally drive to wherever you are and slap you silly!
Given that it's nearly 100 years old, and Savage 99s were generally working guns, it's in exceptional shape. Hopefully the bore is crisp, as well.
The rear apeture sight on it is alone worth probably $200 to $250.
The rifle? In that condition, with a good bore....
It would probably be priced around $1,300 here in Northern Virginia.
The lever should be color case hardened. It's hard to tell the condition of the colors in your photo.
The bluing appears to be in good condition, and the wood is also in good condition. That also appears to be the original finish.
The stock, with that odd recurve on the underside, is known as a "Perch Belly."
Take steps to preserve this rifle. I'd suggest oiling the metal regularly and storing in a climate controlled environment. Even better would be storing it in a gun storage bag that has vapor phase inhibitor protection built in. Bianchi used to make these bags, but I don't know who makes them now.