I see you may be able to just have someone braze/weld the hole and just remove the track if you are lucky, or remove the drive axle/chaincase. Go that route if you can. I just finished replacing mine after barely catching a culvert. Yamaha has a poor design for protecting it from a hard hit. Some have ripped the oil pan open where the molding strikes hang down off the oil pan...I caught the tip of one of them and chipped it off. It took out the rear of the belly pan plate and smashed the exchager into the left side track lugs over the track windows and tore off all the lug tips where the protector is on the exchanger. Replacing it requires removing the susupension, track, chaincase, coolant, and drilling out around 50 rivets and a long cross bolt. I see you didn't hurt your belly pan, but you will probably still have to remove it to get to the hoses and clamps on the front of the heat exchanger... Time consuming..., yes,... hard, not if you are mechinically inclined and have a air rivet gun to put in new steel rivets. I ordered 6 OEM big black ones that go through the plastic at the front of the belly pan. I lucked out and had about 100 3/16 multi-grip rivets that have a grip range of 1/4-1/2 inch. I used steel rivet washers on the rivets in some areas where the total thickness was not quite 1/4 inch. I searched for installation/pics but didn't find any. Definitely make sure what order and direction the gears and spacers go when removing and installing the chaincase... Refer to the apex repair manual in the Sticky section for directions on removal/install and coolant bleeding when refilling the coolant. I did some reading and one person stated his dealer wanted 13 hours in labor alone to do the job....What's labor $80/hr??? get some friends to help, buy a good used heat exhanger for around $180, don't bust the chancase tension adjuster post like I did... You have to heat up that top drive sprocket nut real hot due to the loc-tite and put a crescent wrench on the drive shaft with the brake rotor key in the shaft to keep it from turning. I wedged the crescent wrench against the oil container and used a second crescent to take the nut off...need a fairly big crescent...Hope this helps 