I'd evaluate the existing condition further before I embarked on major repair/replacement.
'Twould take a lot of operation without air filter in an extremely dusty environment to damage greatly piston/rings/cylinder, IMHO (although some insist, without NASA clean room hygiene, the engine quickly becomes toast).
Regardless, a leak-down test will give you an idea of the condition of the rings and valves. Surely, if it's broke, you want to fix it. Just . . . make sure it's broke, first!
[Don't know the meaning of, "sport," as used by the shop--could be, KLX needle. Could be, 685 piston kit. Haven't heard of carburetor slides wearing out, myself; reckon it's possible.]