Painting over OD Green - Do, or don't?

[Receiver Extension]

Hi. I picked up an M&P 15-22 after a few months of drooling over them at the local Academy. I made the last second decision that I wanted a threaded barrel, but the only model they carried with a threaded barrel was the OD green upper/lower receiver variant. I've come to somewhat dislike it on a purely aesthetic level after a while of owning it. I love the rifle otherwise.

Basically, the long and short is that I'd like to paint it just a matte black like a standard 15-22. I've already stripped the rifle down completely since owning it and understand it's in's and out's. What I want to know is the following:

-Could I ruin the internals by painting the outside, given that there's no dust cover?

-What paint should I use?

-Do I need to remove the barrel first to avoid damaging the finish?

Alternatively, anyone in the Kansas City area that would like to trade for a *slightly worn OD Green 15-22 could PM me.

*The white painted lettering for the safety selector and model text ended up strippd by a small amount of oil. Haven't tried re-applying it or anything. I've shot about ~550 rounds through it, which isn't a ton for the amount of time I've owned it.

I've since discovered that I should probably go the Matte Duracoat route, after actually doing some amount of research. Sorry to trouble you all. Trade offer is still open, however

 

[BigWaylon]

You could also Cerakote it.