Many machine shops will do rebuilds if you pull the engine and bring it in. Or they will dismantle it, hot tank everything clean, then mike everything and send it back to you as a kit with all the properly sized new parts.
This lets you do some of the low paying and/or fun work, but have a pro do the stuff that matters.
Oh, try giving it a good ring soak with ATF or MMO first just to be sure the rings aren't just stuck. My first experience with sticky rings was with a bush hog - I bought one and was disappointed to found my tractor couldn't pull it. Sold the bush hog precipitously, only to find out shortly after that power was way down from sticky rings. After dumping some MMO in the cylinders and in the oil it was climbing hills in 3rd that it had been having trouble with in 1st before the treatment.