John Deere D 130 needs new engine

I have a John Deere D130 that threw a rod. Babied this mower its whole life.... changed oil and spark plugs every 50 hours and mowing was lite duty. What went wrong?

Where is the best place to purchase a replacement engine?

I had a 17hp Briggs twin that broke a rod. It did not damage the crank or the bore.
I have ordered a motor from Small Engine Warehouse. Price was OK and they were
knowledgeable and helpful