Hi Dave! Welcome to the forum- when you get a minute, stop by the Intro section, and say howdy.
Back to your question- the part you are missing appears to be the bolt. The good news- they are available. Bad news- they are damned pricey. check HERE: Numrich Gun Parts Corp. - The World's Largest Supplier of Firearms Parts and Accessories Bad news 2- bolts are not just a drop in part- they need to be fitted by a gunsmith. Problem is that the headspace may be off, making the gun eith impossible or unsafe to fire.
Whether yours is worth restoring- from a money standpoint- no. You can put $400 into it, and have a good $250 rifle. From a fun standpoint- maybe. Depends on the condition of the barrel. The ammo these rifles used was corrosive primed- if not cleaned after shooting, the bore could rust, develop pits in the metal. If the bore looks like a sewer pipe, try cleaning, and see what is in there. Good barrel, it could be a fun project.
The wood is something any woodworker could do as a home project- but stay away from sandpaper.
And here is some info on care, feeding and operation of Mausers: Collecting and Shooting the German Mauser 98k (Karabiner 98k) - HISTORY