Replacing with new gears is quite simple. One caution though, there is usually grease in the servo gear area and there may be broken teeth from the damaged gear concealed in it. Remove the grease and check for any foreign parts buried in it as they will jam the new gears sooner or later if left in the grease. Do take a good look to make sure you know the order the new gears have to go back in, best make yourself a little diagram or take a digital picture prior to dissassembly. If all else fails, carefully open up a good servo and use it as a guide for putting in the new gear set.