It's only a bit of a plot hole for this game because we have more access to resurrection magic than a party of this level would or should. Mr. Bones is just offering resurrection for 200 gold, cheaper than a goddamn revivify diamond. Resurrection is supposed to be rare, you can't just pop along to your local temple and pick up a resurrection for little Timmy who didn't make it out of the well.
That said, there's a chance we might be missing something (more than likely, given the fact that we don't have the rest of the game yet). Normally, ceremorphosis take places over a few days to a week, but the game harps on quite a lot that ours is different. Now, remembering the poor woman in the pod on the ship during the intro, she transformed instantly at the push of a button, and it was heavily implied that this could happen to you too.
So, what if your ceremorphosis is actually complete already? If you choose to use the tadpole, or accept the lewd dreams, then you seem to assimilate more with the tadpole, which might mean that by the end of the first act you are actually ceremorphosis-ed, just in a special way that has left your body un-transformed, at least for now. Congratulations, you're an Illithid sleeper!
While this would at least cover the resurrection problem, it creates some of its own, if the ceremorphosis is complete, your tadpole would be gone, absorbed into your brain (technically it would become your brain), but it's clearly still there, because you can still have people examine it even after you hit maximum tadpole assimilation.
