Hi Cruiser348.

There's a couple of aspects to your question that need to be addressed, so bear with me, ok?

1) Stitching: Typically with leatherwork, a waxed thread is used, however there are several tools that are also required if you wish to replace the lost stitching. Specifically, you would need a diamond-profile stitching awl to make the new hole, a round-profile awl to widen the new hole, a needle (funnily enough) to push/pull the thread through, and if you're as finnicky as I am, you'll want a stitching wheel to measure out the spacing for the holes so that they're evenly spaced. So far I've outlined about $60 if you were to purchase all this from Tandy Leather Factory. You may instead wish to seek a cobbler and see if they'll do the work for you.

2) a clean edge: Any very sharp knife will do the job, although you'll want one with a strong blade. If you're not interested in doing lots of leatherwork, a Stanley utility knife from Home Depot will do the job nicely and can be added to your toolkit for use in other jobs once you're finished altering your belt. I would recommend that you mark where you want to cut and use a straight edge (if you want a straight line) rather than "eye-balling" it. I can speak from experience that "eye-balling" never works out very well. If you want a curved edge, make sure you use something to trace around, and then use your Stanley knife to cut the leather. Also, make several passes. Don't try to cut it off in one go, 'cause you'll inevitably make a mistake and either cut off leather you wanted to keep, or -worse still - cut yourself! Just carefully trace the line with your knife, and then go back through the groove again and again, until you've cut through the belt.

3) finishing the appearance: Look at the edge of the belt as it is now. Is the edge rounded or square? If it's rounded and shiny, you may wish to "burnish" the leather after you've cut it. That is, take a very fine amount off the corner of your cut, and then wet the newly cut leather. While its still wet, take some stiff cloth (eg: denim, canvas, etc) and rapidly rub the wet edge of the leather along the newly cut edge. Done right, this will cause the edge to become smooth and slightly glossy, which is what leatherworkers call "burnished". It can make your work look a little more professional.

If all my rambling above sounds like I'm talking Greek, you could always seek a leatherworker to do the job for you. I'm in PA, so if you exhaust all your resources and still want it done, drop me a line and we'll see what can be done.

regards
Hachiman