One W is a total non issue. Don't even think twice about it if that's what you feel you need to do to preserve your GPA.
I happened to have one W on a prereq and received numerous interviews. Never once was it brought up and I doubt it was even noticed. You have to keep in mind it's going to be buried amongst all your classes so it's not going to be in the ADCOMs' faces anyways.
i had a handful of W's for various reasons (couldn't understand a foreign professor), advised to take classes that I found out later I didn't need ect. My gpa is 3.8. I got an interview, but I am still very worried that the W's will affect my acceptance.