Refinishing a cab is a lot of work, and cutting costs does sound appealing, I get that, And most likely you would be fine if you were to use a heavy bodied paint (although you might see some of the sanding scratches and problem areas underneath).... Sanding it down does offer benefits in terms of quality however, primer is designed to fill problem areas, and by taking it down to flat you use it to its full benefit, a chance to check it over for issues, And creates a even bonding surface for the next coat... It will only be nicer if take it down and recoat, If its good you can thin your next coat down a bit (or use a sealer) to help minimize any orangepeel before you finally do the color.