Wait, stop...don't throw away that old gas grill because the burner bar is all rusted or collapsed. Replacing the burner bar is pretty easy and cheap. Universal replacement bars can be purchased online or at most hardware stores for less than $30 and they include all the parts needed.
The outside of our old grill was fine after being outside for almost ten years but the burner bar was shot. After getting tired of burnt food and only being able to cook on one side of the thing I replaced the bar. The process is outlined in the linked video.
The one thing to keep in mind when purchasing a replacement bar is to make sure that the flexible tubes will fit through the existing holes in the bottom of the grill. If they don't fit, like the one that I installed, then a few cuts with a rotary tool or hack saw can open up the space for the gas lines.
Before installing the new burner, a good scrub down and tightening of all bolts will make the whole thing look almost like new. A few sprays of black grill paint would truly make it look like it was just purchased. And all can be done for less than $40.