I would hold off on the diamond plate...unless you're planning on adding a 302...those plates are nice, but they add weight...and a 2.3 needs all the help it can get to stay at highway speeds...
But they may add a layer of protection if you live in an area where shootings are a regular event...I was thinking of doing that on the outside of the door at one point...but backed off...the weight...oh, the wait...