I'm doing the succubus quest right now, and had some trouble finding stuff and thus looked at a guide.
In this guide they mentioned surgical tools, but where is this mentioned in-game?
At what point does someone suggest to look for them?

Geralt goes, "There's something embedded in the bone" when you're examining the arms of the dead body, and then says, "I can't extract that without special tools."

Yup, 227 is right on that point. In addition, you purchase the tools from the female store owner. Can't remember her name, but she's the one who also offers you the haircut service. The tools allow you to gain remove the object embedded in the corpse.