In my most recent playthrough I went on board the Dainty Sload before ever joining the Thieves Guild and ended up killing a few of the Corsairs before leaving. I'm curious as to if this will render completing the later Dainty Sload quest for the Thieves Guild impossible or not. Thank you in advance for any help/advice.

It respawns. You could do a 30 day wait before running the Theives Guild quest just for extra measure.

Thanks!!!