Way too easy to do this modification.
1. Frustrating trip to Walmart to buy the Krylon Gloss Black Paint for Plastic for $5. Gloss black to match the gloss black window trim from the sports package.
2. Removed Grills without even opening the hood of the car. Required reaching through the grill to unhook the lower clips, and using a hook shaped tool to assist in unhooking the top clips. Way easier than I expected.
3. Separate the outer ring of the grill from the inner slats by unhooking the clips.
4. Wipe down the outer silver ring with denatured alcohol.
5. Spray on 3 coats
6. Reassemble in the morning and install.
Looks just like stock black kidney grills for the 335is but costs $5 instead of ~$130.
Thanks for the DIY, it helped a lot.