I wish I had a nickel for every time I've heard this.
Agreed.
Even if your teacher is terrible, it's a math class - just learn it from the book. Read it multiple times and work the example problems until you understand it. (And I say this as someone who is innately lousy at math - with some work, you can become good.)
That said, if you seriously believe you can pull off the C, that would be way less hassle than having to retake the class. (And I understand being worried about having it be a D, but if your other grades are all A's, it probably means you have the work ethic to avoid this. Make Calculus your first priority, bring the grade up to at least a C, and be done with it.)
Either way, you're going to have to explain something on your transcript. You can either:
A) Retake the class, but you'll have to score very well the second time in order to negate the W that you'll have to be ready to explain at all of your interviews.
or
B) Just take the C, do no additional work, and move on with your life, being ready to explain the C at interviews.
For me, I think option B sounds much easier. Lots of people get into med schools with C's - it's not a big deal at all. But it would be an incredible amount of pressure to have to retake a class that's already difficult for you knowing that if you don't get improve significantly you're going to look like you can't handle the material.
But whatever works for you. Those are the options as I see them.