Welcome to the Bladeforums, and the KA-BAR forum.
Mineral oil is a great choice. I am assuming the black blade coating is still intact, which means you won't need very much at all. The only are on the blade that will need any protection will be the edge.
You can apply a very small amount of oil by using a Q-tip. Simply wipe along the edge, and you are done. Fear not, mineral oil is safe for ingestion, so, if you are using your blade on food.
I prefer to use a guided sharpening to sharpen my knives, the one I use, is a KME sharpener. Its a great and easy sharpening system. If you are more of a free hand kind of sharpener, I would recommend a 9" Norton benchstone, and a smaller fine india stone to keep with the knife, for field sharpening.
You are going to want to maintain as much symmetry on that edge as possible. There are several great tutorials here on BFC and youtube, I recommend you spend some time familiarizing yourself with sharpening in general. There is a book I would recommend, Sharpening Made Easy by Steve Bottorff. Its a great book, and very inexpensive.
As far as the serrations are concerned, you will come across special stones, and equipment that make sharpening them easy.
Good luck, and stick around, there is a ton of great information here.
Moose