Mine didn't do much of anything and I never saw him. Others here love theirs. I say get a bunch of nassarius snails (they are tiny - pea sized) and other sand sifters.
Nothing should happen if a cuke dies other than what would happen if a similarly sized fish or invert died. The animal in which you are reffering to is the sea apple which will poison your whole tank if he dies and you do not take immediate action. This has been discussed quite a few times and you can find supporting info if you do a search for this subject. I personally do have a few cukes and am sure they are doing just fine (despite never seeing them).
The whitening effects of ingesting sand, sending it down a long acidic gut, and then shooting it out the other end are truly difficult to replicate. Certainly beyond the capabilities of those animals that simply burrow.
All hail the mopping cuke. It does something willingly that I am not willing to do myself.