that's cool steph. I almost bought something similar. I saw a Kenwood one on Ebay almost identical to it and wanted to do the same thing, but since it came from Japan I didn't know if there was going to be any troubles installing it, troubles with language etc.
Kinda wish I got it now. Looks good. I hate having that extra din in my dash, and not having anything to put in it.
Personally, I'd leave the black part alone. Looks fine. Only paint it silver if you can match it identical to the rest, otherwise, it'll look kinda strange.