First, congratulations on your fine purchase. Even though I've never shot that particular CM, I think you are going to like the bow.

Personally, I'd wait until the bow arrives before buying additional arrows. Shoot it for awhile and see what happens to your draw length. A few people don't lose any when shooting traditional equipment and the only true way for you to know if you will or not is to actually shoot the bow. You will be focusing on form and release more than accuracy at first anyway so your old arrows should be fine at first, but then you'll want to get a set made for the bow that will fly well from it. Oh, good idea to get them fletched in feathers.

My lady shoots a 28" 1916 with 125g point from her 45# at her draw CM hunter II with a dynaflight97 flemish twist string. When I shot the bow @50# the bow liked a 55/60 or 29" 2016 both with 125g point. It is really a personal thing as to which arrow your bow will like. If you and another person were shooting the same bow and had the same draw, you would still release the bow differently and would probably use a slightly different arrow spine.

Patience and fun are the key to learning to shoot traditional equipment. If you havn't already done so, buy yourself a book or two on shooting. Try out the different methods and then come up with your own that suits your body and attitude. Or, stick with one you like and works for you. Most of all, have fun. That's what it is all about.