John Deere 14SB Problem Free No More

If there is anyone that can help. I have serviced my John Deere 14SB numerous times throughout the past. It is pushing 23-24 years old next year and it has never had a problem until today. I used it to do the trimming for the lawn, it sat for awhile cooled down, then it was cold, so I wanted to change the oil because it has been awhile. Fired it up to warm the oil so it would drain easier. Drained it out, tightened the drain back up, went to fill it with oil. So far no problems. As soon as I am ready to start it, I look down and there is oil gushing out of the bottom. I did not start it after realizing this. I cleaned debris away (oil and dirt gunk) and I found a crack in the base, right behind the drain area that I believe runs a little down under the base, and up the side.

I felt and feel awful right now. I have been frantically searching this afternoon and evening for parts. Luckily, if there is any good news, its only the base that is cracked. All parts inside should be fine.

Though it might be tricky, can the base be replaced with a new/ used one and re-attached to the crankcase, upper part of the engine? This mower means a lot to me as it is my grandfathers. Where do I even start with this repair?

I figure it was only a matter of time before it had a major problem such as this, the older it gets the more fragile it becomes. Just very upset about this and want to do everything to fix it, if possible. I should have left it alone, ugh!