Small Engines (Lawn Mowers, etc.): Honda Oil Leak - Blown Seal/Gasket?, oil drain plug, seal gasket

Question
I have a 1992  (I believe it is the correct year) Honda HR 215 AE   HX model lawn mower that I kept in excellant running condition. The engine is a GXV140 type.
The other day I was using it and it started to make a sputtering sound so I shut it off immediately. I had just filled it with gas so I knew that wasnt the problem. I checked the oil level and it did not register any level. I then added some but it still did not regester oil level. I then added alot of oil and looked underneath the cutting deck and the oil was coming through the deck onto the ground. Please not that the oil drain plug is on the side of the unit. Is it possible that i blew a oil seal/gasket?
Questions:
1) Would the oil seal/gasket be difficult to change? I am very handy and do most of the engine work in the past.
2). What are the chances that I ruined the motor due to the oil all leaking out? Is there a way to test the engine before I have the expense of putting a new oil seal/gasket on the current engine then finding out the engine is bad?

I really love this mower and would like to still keep it going.
Thank you in advance for your cooperation.

Answer
 Hello Thom:

 It Sounds ike the Lower Crankshaft Seal is Blown. There should be an Engine Type Number to go with the Engine Model Number GXV140. If you can locate this Type Number on the Engine, then Go to this Addy http://www.honda-engines-eu.com/en/service/spareparts/heepartscatalogue/index.js... and Select the Engine Model and Engine Type. Then Click Search. This will take you to a Breakdown of the Engine. If you Didnt Allow the Engine to Run Long after the Oil was Lost, then you should have No Worries. Any Internal Damage wont be Known until the Engine can be Safely Started to see if the Connecting Rod or Cylinder is Damaged. If you are Doing the Labor Yourself, then the Cost of the Lower Seal Replacement is not that Expensive and with the Breakdown you should have very little Problem doing this Repair. Hope this Helps. Let me know what Happens, Please. I Enjoy knowing the Outcome. Thanks.

 Good Luck

 Respectfully

 John