Ahh that sucks man, I've had pretty much the same damage. You can definitely DIY this between 800-1500, depending on how many new OEM pieces you get.
Bit of a delay since the last update. My sister got married this past weekend, so I've been tied up the last month with that. Now that the wedding is done, my attention can turn back to this heap. A couple hours in the shop turning some wrenches, bagging and labeling parts, and jamming out to Spotify, and she's 80% stripped down. All peripherals pulled and cases split. Just have to pull the connecting rod/piston assemblies, shift shaft and transmission, and she's ready to replace the bad parts, and reverse the process. All in all, didn't look too terribly bad. First, pulled off the oil cooler, as well as all of the radiator piping on the front of the engine. Stripped out the clutch pack, basket, and hub. Everything looked good here, with very minimal wear. Pulled out the pickup coil, and was left with a bare right side of the engine. Next stripped the stator, starter, and the accompanying gears. Took off the oil pan, strainer, then pulled the oil pump, as well as the various tubes that route oil through the engine. Final step of the night was to go through the sequence of systematically removing the bolts that hold everything together. A few light taps with the handle of a mallet in a couple spots to break the seal, and she came apart easily enough. Hoping to have parts ordered in the next week or so, wait for shipping, then put it back together. Assuming I don't run into any unforeseen issues, I'm hoping to be back up and running around the 4th of July.
Day two of tear down... First, I removed the countershaft assembly, then I pulled the shift shaft along with the shift forks. After the upper shift forks were removed, I removed the retainer plate for the shift drum, and was able to remove it, as well as the lower shift forks. With those items out of the way, I was able to pull the main assemly. Next up, I pulled the connecting rod end caps, and removed the crankshaft. With that gone, I was able to remove the connecting rod/piston assemblies. You can see the damage to the piston on the far right. Not much damage, luckily, but enough. Now to get everything to the parts washer, cleaned up, and order the necessary parts to get this thing back together.