in advance please forgive my lack of technical terms. I replaced my cas with a used one about a month ago and it was quite easy. When you remove the old cas you will see that there is a shaft that the cas connects with. The two pieces together will form the complete shaft where they come together. They are cut in halfs at the tips where the two meet ( one side on the cas, the other permanently attached where you insert the cas). So just look at the orientation of the old one right when you pull it out withouth rotating anything and get a mental picture in your mind for when you put the new one in. Good luck.
Tracing the old one will have no significance of the alignment of the shaft of the CAS to the mating spline of the cam, furthermore it will have no significance of actual timing.
Sleepybp is correct, just note the position of the old one and also look at the shaft on the cam. You will see the half moon shape to give you an idea of where to position the shaft of the CAS to get it to line up. Once you have it in place, set it dead in the middle and then use a timing light to properly adjust the timing.
OK - I was just referring to keeping track of the position for the timing setting. Some don't have lights to run a final check and unless the CAM sprocket moves a bit -- setting should come out pretty close.