Don't do it yourself. the real method was already partially explained, they actually spray a metallic 'primer', then copper plate it, then nickel plate that, and finally chrome it. REAL triple plate! i have done it, no problems. to a small degree the plastic item can 'flex' and no chipping or cracking will occur. a plastic fan shroud for a GM engine will run you about $350-$400, my advice: save up if you don't have the cash and DO IT RIGHT. no at-home-do-it-yourself kit.
try
www.paulschrome.com
they are in pennsylvania, if you must use someone closer to you ask paul's for a referral. but that's why u.p.s. was invented, so you can ship your part(s) out and back. paul's gives free estimates, too.
and no, i don't work there. i do recommend them, however. if anyone needs more help in this matter, just e-mail me. i'm here to help.