lol, you love your positive G's now... wait till your first session of steep turns and see how comfortable you really are with them then ;D (jokes, I was uncomfortable for the first couple but you'll get to love it pretty quickly.)
I don't know what you mean by "quick, nose down manouvres", and someone else out here might have more of an idea about what an instruvtor might be doing in a TIF, but I can tell you that you're going to run into slight momentary negative G situations all through your flying. Even slight turbulence can cause negative G... and somedays it'll be pretty rough. Seat belts low and tight work wonders, and you'll get used to it all pretty quick.
(Older and Wiser: Correct me if I'm wrong, Again, Pre-PPL so not an expert by any means)