No! Leave him be, I will add more details, but I just want you to see this first!
Okay, I needed to get that out there first. Leave your hermit crab alone and make sure all the parameters are fine in the tank (temp, humidity). If he shed his skin he was just molting. It IS possible that he died in the process, but if you disturb him now, and he is alive, you may end up stressing him and killing him.
If he has taken on a very deep color, it is possible that he molted a few days ago, as when they first molt, they are soft looking and usually a light pinkish color.
It is very important that you
1) leave him be (i cannot stress that enough)
2) leave his molted exoskeleton ("skin") IN the tank, as most crabs will eat a good portion (if not all) of their shed "skin", this is a good source of calcium and other nutrients for them as their new exoskeleton hardens up.
3) offer him good fresh foods, with calcium being a priority (offer egg shells, broccoli, etc.) and water (both fresh distilled water and distilled water mixed with aquarium salt, NOT table salt)
If he is dead, or dies in this process, you will know it, as he will take on a strong dead fish smell. Until that happens, don't give up hope on him.
Check out the link below for more info on crabs.
edit - also feel free to message me if you need anymore help.