Uhhh - you've got some issues there. In fact, I don't know exactly what to recommend. Obviously, it has great sentimental value to you - and I certainly respect that - otherwise I'd suggest you dispose of it as not worth fixing.

The receiver has been drilled and tapped for a 'scope mount. Do you have it, or is it missing? I do not know which mount it might have been - most used four screws. If not then at least putting screws in the holes would improve the appearance. You are missing the rear sight and hand-guard (which isn't really required, for a shooter. The barreled action (Model 1898)  does not match the stock (Model 1896). The barrel band is incorrect, and on backwards. That model did not have swivels or a sling, but if you want one, I'd suggest getting the proper rifle style sling fittings - the ones you have are homemade. Fixing that would involve some woodworking skill. The stock has been excessively sanded, which has damaged the profile - this is not fixable.

If you skip the handguard, you can use any Krag carbine sight - the Model 1901 is the cheapest and easiest to find. The correct Model 1896 rear sight is $500+ though you could use a Model 1896 rifle sight and no one would know. The proper sight would also require the proper band which has protective horns.

Will the rifle stay cocked when the bolt is closed, and does the trigger release properly? I ask that because it looks like the bottom of the cocking piece has been ground off, perhaps intending to make the gun non-functional. I see from one of your pics that it apparently does stay cocked, but the cocking piece definitely seems damaged.

You know, I think I've talked myself in a circle - the best idea would probably be to mount Grandpa's gun in a nice frame and hang it on the wall as a tribute - then, use the money that you really - when all is said and done - would be wasting, chasing a very impractical dream, and buy yourself a nice Krag.

Just my $.02, based on 45 years of collecting.