I'm assuming it's an older bow so first of all I would get a new string. B-50 Dacron 16 strand string for that age. Older bows have a tough time handling more modern string materials. You would probably be good with a 48" string if it's a 52" bow. General rule of thumb is 4" shorter for recurves. As far as poundage, most people need to start low 40s on poundage. Once you get it strung, you'll understand why he said that. I've got a Widow that draws 62# and another that draws 65#. The one I now hunt with is 51#. If your length is 28" which is really common, you can probably get some 125 grain field tips with 340 carbon arrows and be good. If you go any heavier on the point weight you'll probably need to go with 300 spine. That said, every traditional shooter is as different as finger prints. You may be able to go with 145 grain tips without a stiffer spine. I would test 340s with 125 grain tips first though.

Once you get it strung, don't put a nock point on. String it and let it sit a few days inside as the string will stretch. I would even draw it some. Once it's stretched, then put a nock point. If you don't have a bow square, get one. I'm not sure what the recommended brace height for a Bear Kodiak Magnum is, but you should be able to find that. Don't go by that as religion. All that means is the manufacturers recommended brace height. Don't be afraid to twist/un-twist the string to adjust it if they bow isn't shooting smooth.