I went ahead and did a tutorial on how to carve a complex shell, although I expect there's not a lot of interest in it. Instead of putting it up here and on my web site, I only put it on my web site.
I would not recommend attempting this shell until you're able to carve the simple shell and the second shell to your satisfaction. While it may not look a lot harder, there's a number of techniques which a beginner will have trouble with. Like many things, you need to progress from simpler things to more complex things.
Good luck!
Mike