I suspect there are many bearings inside the trans/engine.
So he's going to put a piston in it as well. Hmmmm did he do a compression test to see if it needs a new piston/rings hone or bore job ?
Does he plan to hone the cylinder or bore it to the next size over if needed?
Is he going to check and/or adjust the valves ?
So piston/rings, gasket set and some bearings should be a couple hundred bucks plus labor cost maybe, well good luck.