Your panel is ok. Not much of a damage. Won't really change perfotmance. Any used one will be already with damaged lips (yours are still there). So unless OCD hits you hard just leave it.
For stones - your condenser gets first hit, so your radiator is protected)))

 

I just ordered a replacement for my '02 330ci for my clutch fan and aux fan delete. All of the soft rubber edges were disintegrated which I think may affect air flow through the grille and lower section of the bumper. If you replace yours, order 4 new expanding rivets (51718229003) as they are almost impossible to remove without destruction.

 

As to the debris, if you are really concerned, 3/16" hardware cloth attached to the back side of the grille and bumper intakes is probably your best bet.
1/4" if you live somewhere with huge hordes of mosquitoes.

Somewhere around here I have a picture of a 10x60mm Nissan bolt that made it through the grille (forcibly)
of the E30, and distorted the mesh so much that the bolt was hanging just an inch from the radiator.
But didn't hit it...

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