diablo9420

Hi, I just got a E-Revo brushed last week, and I think I messed it up already. I was showing it to my buddy and he told me the gear mesh didnt sound right (I never moved or touched the motors yet) so I decide to take a look at it today and my spur gear seems to be out of round, is this normal or do I need to replace it? The kit came with a spare 62t gear (originally a 68t) and it doesnt seem to have any run out what so ever. Im a total amatuer at this, never really cared to fix anything on my old rc unless it was physically broken (junk Exceed car), but im trying to do it right with this one, already replaced front drive shaft and front a arms (didnt notice a rock sticking out of the ground) and im waiting till tomorrow for my new battery (original melted 3rd run of the car, traxxas is semdimg me a replacement). Anyways back on topic im going to use the 62t gear until I get some feed back and make it to the hobby store for a new gear if need be, but when putting the gear back on theres the spring and nut that hold it to the drivetrain, how tight do I put that?