Should i trade my sony a230 with 18-55 mm lens for a nikon d80 with a 28-300 lens?

The question pretty much says it. Should I trade?

No, if you want a longer lens, save up for one, and the 28-300 won't be as good as your existing lens.

You could probably pick up a used Minolta AF lens fairly cheaply on the used market, just try before you buy and get a warranty.

Sure if you need the extra reach of the 28-300 mm lens. That lens is a FX lens so if you ever buy a full frame Nikon (D700/D800/D3/D4).