OK, here's the problem with ALL the details. Murry tractor 17.5/42. I did an oil change and possibly added too much. White smoke came from the exauhst flooding the yard in smoke. I emptied the oil, cleaned the plug, and let it sit for 2 hours. Then added in oil, (synthetic) probably shouldn't have done that. Only added about 1/4 quart to be safe. Started right up with some smoke burning off. Shut it off and restarted 3 times. On the fourth time it would not start. Flywheel was practically frozen. Could turn by hand but was incredibly hard to turn. When starting wheel moves only about an inch. Still incredibly hard to turn by hand. Should I have a company repair or should I buy another. I tried pulling up on the fly wheel but it will not budge. 3 acres of lawn about a foot high now. Any info will help. Limited tools and knowledge for lawn mowers.

Use only 30w sae oil in this engine... 10w 30 will cook and become a sludge

Sounds like you have done broken a connecting piston rod, the piston is probably "FROZEN" to the cylinder wall and as you try and start the engine it is moving the connecting rod up into the cylinder and striking the piston. You should have never only added 1/4 qt of oil. Most of the larger engines require 48 ounces, which of course is 1 1/2 qts. Remove your cylinder head(s) and see if you can make the engine turn by hand, if not see if you can get the piston to move after spraying with a good lubricant. You may be able to repair the damage, but if the cylinder wall is "GAUDED" i would probably purchase a new engine and start over.
Try and locate an engine at :ruralking.com
Rural king is based out of il and seems to have very competitive prices on engines, and small engine parts.