I am always suspicious of percentages people pull out of the air, getting an actual measured percentage is a several step process. From what I could see, that sprocket looks decent (sprocket teeth should NOT be sharp), and the pin and bushing I could see didn't look like it had been moving around?
Check all the oils, level, not milky, not dirty feeling. Think there are 2 dipsticks through the floor, plus the engine one.
I would want to start it it's first time of the day to see how it starts cold, then run it enough to get it all hot. Check engine blow-by. Make sure steering clutches don't slip, disengage when they should, brakes work.
You can add a grapple, but it will take welding and splicing into the hydraulics, not just buying one and plugging it in.
I am seeing decent D21a-6s with a 6-way blade going for $10-12,000 around here, loader probably less?