Substituting hazelnuts for almonds, baking
According to the Mayo Clinic, hazelnuts are somewhat more fatty than almonds, per ounce by weight (the range is for whether they are roasted or not):


Almonds - 14 - 15 g 
Hazelnuts - 17 - 17.7 g 


As might be expected, hazelnuts are slightly lower in starch.  These is unlikely to make any practical difference in the recipe, as both are fairly close.  

You should be able to use them close to interchangeably in recipes, although their flavors will be deliciously different, of course.

As for peeling hazelnuts, there are many methods.  One of the more effective techniques, which will work if you are going to toast them lightly afterwards is to blanch them in a baking soda solution.   See, for example, this article from My Baking Addiction with a video of Alice Medrich and Julia Child embedded demonstrating the technique.