I painted my front grille, Valence, and the whole inside on my Ranger, and I painted the cheap steel wheels on my Jeep and a friends Ram. They all turned out great
And this Jeep looks So Cheap and Crappy you could never tell, The fenders were faded out and that the original color on the hardtop was grey. I know you cant see the wheels but they look very good.
Okay to the OP this is very doable but you will have alot of prep, The grill will take about 3 hours to remove prep/paint, from there it needs to stay inside for at least 3-5 days to harden before you put it back on. Take it off, sand down real well (you have to eat through to plastic) now switch to prrogressively lighter gritt to smooth out rough spots, now clean with Acetone. Fom there throw down 3 light coats of adheasion promoter (I use Bulldog) then lay down two coats primer, 3 coats black, 1 light coat sealer.
Valence use the same steps as above only you dont have to scratch as much but it still needs to be rough.
The wheels need to be scuffed up pretty good once again you need to try and eat through the chrom finish on them, now clean them with soap and water, when there dry use acetone. Tape off tire and open slots on the back. Instead of adheasion promoter use a Self Etching Primer 1 good coat then 2 light coats of regular primer just to make the surface smooth so you dont see sanding marks. Now do 3-5 light coats of black and one light coat of sealer.
Chrome bumper I would use the same as above, but rough them up even more go through the chrome.
If you have any more questions feel free to ask