You could paint it black, and it is possible to get a factory look at home, but it isn't easy. Humidity and temperatures will be your enemies, and can lead to bubbles in your clear coat. You would be better off letting a body shop do it for you if you want the best quality. You could save some money and do all the prep work yourself, as that is usually the most labor intensive part, and therefore the most expensive.
That ad says it is for a 2500. I am not sure if the HD beds are the same as the 1500's or not. Do you have a 2500 or 3500?
I believe they are they same.
Like he said prep is the more labor intensive part. If you prepped it I would think it would be quick and fairly inexpensive to have it sprayed
Remove the hardware, badges, mounting hardware, and tailgate cap. Then sanding, sanding, and more sanding to get through the clear coat and into the base coat. Then if there are any imperfections, you can use body filler to smooth it out, then sand that smooth. For your sanding, you will want to get a block that is at least 12 inches long, and preferable 16-18 to keep things as even as possible over the larger areas. Then sand with just some sand paper in the crevices. There should be no gloss to anything anywhere. Then just make sure the surface it clean and free of dust or oil, including from your skin.
If you go with the painted gate you would probably just have to remove emblems and anything else you wouldnt want sprayed and just scuff the white
Already having paint on it it may take a few coats to get to match better
i agree i paint. don't sand thru the clearcoat.(on a apinted part) use a grey scuff pad (the red ones work but leave more scrathes) available at any paint store and some comet or ajax powder. you can wipe it down with gas a few times first, to remove the grease and wax or buy the stuff made for it. wax and grease remover from the paint store. this is the most important thing to stop the bubbles in the paint. then scuff it with ajax and water wash it clean and spray it. if you use a spray bomb don't do it when it raining or looks like rain pick a dry day. if you have a good painted tailgate there is no prep time for a bodyshop. it will only pay about 1.5 hours. if that to refinish. just be careful pulling emblems they are plastic and break easy you can cut glue with wire like a guitar string or razor blade if you are careful you don't even half to remove whats glue is left on tailgate after painting just use it for a guide and use platic emblem glue and glue it back where it was. you'll have to tape them in place while the glue dries.
When I detailed cars I found the easiest way for me to remove emblems with what I had was to heat them a little bit and slide a piece of floss behind them. The Ram head has pins behind it that make it a little tougher to remove but easier to put back on