BudsGunShop.com - Fore Grip

Yes, this the foregrip has a picatinny rail underneath. So you can easily remove and replace this foregrip with one of your choosing.

Felipe, yes it is attached to a pic rail under the barrel and can be taken off by removing one screw. Any vertical grip that can be attached to a picatinny rail will work. Be sure to know your state laws first, an angled grip may be ok, but not a vertical grip. In CA vertical foregrips are legal for pump shotguns, but not legal for semi-auto shotguns. budsgunshop.com/product_info.php/products_id/36812/utg+rb-fgrp168b+utg+vertical+foregrip+ar-15m-16+polymer

yes it is attached to a rail

Felipe, yes you can Sir. The angled grip is attached to a 2 inch picatinny rail. youtube.com/watch?v=C_TrYdEDKes

It doesn't appear to be replaceable as it is not attached by Mlok or Pic rail, you could remove it but not sure that any others would fit.
Better pictures of how its attached on SDS website