Dave- The K-series engines typically developed wear midway down the cylinder walls ('taper'). Most of the time, a simple re-bore (to 0.010" or 0.020" oversize) and a new piston and ring kit will solve the oil-consumption problem... but before you do that, take the crankcase breather off, clean it out, and reassemble. If the engine stops breathing oil and spitting the dipstick out, the problem was more likely a breather than cylinder wear.
As for rod-bearing wear, typical method of solving is to grind the crank to 0.010" undersize, and purchase a replacement connecting rod, however, I've never had to do that- I simply cut down the rod-cap, polished the crank, and reamed the crank to proper fit. I haven't come across any valve or guide wear, just ground valve seats a little.
For rebuild parts, you can use authentic Kohler parts, or aftermarket replacement parts by STENS... they're less expensive, but still good parts.
The other thing you can do, is check the For-Sale segment of the forum... some guys here find rebuildable engines, and give 'em a full going-through, then post 'em for-sale for much less than a Kohler Replacement Engine... oftentimes, much much less than if you were to take your engine to a shop for same work.
Terry- the 'Decompressor' translated literally, is the French term used for 'Automatic Compression Release'. Just be glad he didn't refer to L'Embrayge... Hydros don't have one!