Yes, it’s pretty much that simple but you will also need to change your stabs since there are now two keys to stabilize. That means you might have to take pretty much the whole board apart depending on what kind of stabs you have. It will likely be 2 × 2u stabs

I put my arrows on a layer under hjkl but I’ve also heard ijkl and wasd are popular for that

Check out the quefrency 65 rev 5 by keeb.io. It seems to match your criteria pretty well. For palm/wrist rests I use two purple squishies