Check out the following thread on making Shipsets:
Ship Sets:How do you do them?
I'm probably a pretty much average user, but have no previous rendering experience. DoGA was about the easiest program to use and it didn't take much time to get something to look how I imagined it. In my opinion it is a lot easier to use than Photoshop or PaintShop Pro. Plus, once you save a ship in a 'class' you can use that as the basis for the ships around it in the same class and just manipulate the pieces. Making the Racial pic was the most difficult thing and is something I'm still trying to make look more 'real'.