Molds?

I want to make a Fiberglss copy of my car's grill but without the oval for the emblem and without the vertical supperts. (note pic at botom)

To do this I know i need to make a mold of the grill and then i can use clay to take the oval out and match the rest of the grill. My questions is how do i got about making a mold? i know i need some kind of liquid and set the grill in it and let it dry. Then remove the grill. What should i use? I was thinking just some kind of clay. Make a box for it and push the grill into. Then i can bake the clay and use that.

I was thinking about two part foam. But if it covers over the entire grill (Fromt and back) Then i will need to cut the foam and i might mess up the grill or mold.

Anyone have any ideas?

What i think would work best is if you first found out how much a new stock grill would cost, my guess is around 50 bucks, and contemplate about having to buy a new one if you mess up. Once youve decided ur willing to try something I suggest  just unmounting the grill from ur car and physically cut out everything you dont want with like a reciprocating saw or dremel. Then get some bondo and go to work makin it all smooth again and get it painted the color you want. I think makin a mold for it would be pretty hard for such a large piece and definitely more expensive.