Can't picture it in my head but i'm guessing it's just a breather pipe that runs from the cam cover to the crank case? inwhich case it sounds like the pipe is probably blocked and sucked itself in kinda thing, take the pipe off and clean it out, if it doesn't return to shape then replace it.

Shouldn't need special tools as such although the hos clips will be tricky unless you have some grips/pliars handy.