RE: 30-40 Krag
Sporterized models are sitting in the used gun racks around here for $250-$300. To do much updating would probably cost a significant amount more than that. (Reblueing, re-stocking, etc.). I guess my advice to you would be to leave it alone. You would probably be money ahead in the long run to buy a new or very nice used gun in a cartridge of your choice.