As I understand it you have a PVC pipe that comes from the sump pump and at some point connects to a "Y" with a valve so you can either direct the water outside or to the waste pipe in the cellar.
If this is so, I would cut the PVC pipe that goes to the waste pipe about 6" from the "Y" and cap it off with a PVC clean-out type, cap. (You never know if, or when that might come in handy)
Now, where it comes out of the waste pipe, I would do the same thing.
If you own a hack saw or can get one from a neighbor, you are only going to have to buy 2 clean-out caps and the proper PVC cement.
I would never remove the sump even if the cellar is fixed. You never know!
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