How do I install Repair valves and push rods in Briggs & Stratton 18.5 hp motor for lawn tractor?

Remove the head, using a valve spring compressor, remove the keeper and spring, remove the valves. Pull out the push rods, reinsert, and reverse directions. Be sure to adjust the valves, after five minute warm up. ( warm up the engine, not yourself, Ha Ha) just a funny note there.

Broke a valve, installed new an lapped, set clearance to specs, won't start, backfires and shears flywheel key but turns over fine otherwise ,rods are straight, no signif damage to inside??