Ed, have no fears about being too close to the original. If you copy the master, you will learn how he worked, what tools he might have used, and if your work came out anywhere close to his, you'd be blessed with good fortune. I am glad to see you plan out your project so carefully. This is the best thing you can do for your carving: decide what you want ahead of time, long before the chisel touches the wood.
What you are doing here requires several layers of depth; you will surely lose parts of your drawing. As you carve along you will find that your drawing has been cut or worn away. Use your camera as a tool for carving: take a good front on-shot, and print it out. Paste it up near where you will carve, and refer to it constantly as you carve.
Best of luck, I look forward to the results!
Tom