Nice job on the engine bay--I bought some dress-up bolts too, and found they make a nice touch. I wonder if you just treat the leather covers with a product that you spray on boots/shoes--I've sprayed mine (boots) with some stuff to keep the winter snow/salt residue from eating away at the leather--works great, but I can't think of the product's name. And those Heko visors--great to have to keep the water from coming in and dripping on your arm rests, plus, they look sleek!
Scotchguard for leather, Neverwet for fabric or Mink oil might protect it and keep it looking nice.
I love those Heko visors, they are on the wish list for The Speed Bump.