I knew it was going to be the wrong color, because it only came in black, but how much work do I need to do to strip down what is there to repaint the new fork I bought. Can I just rough up the surface and paint over? My results I'm looking for are a nice simple solid silver paint job that won't scratch if you look at it.

What is the fork made of? If it's steel, particularly welded steel, there are a lot of options including powder coating after stripping the original finish. If it's carbon you have very limited choices as you can't use chemical strippers and it won't take the heat of powder coating. For carbon, just scuff up the surface with fine sandpaper and respray.