It can't remove gyno...only a surgeon can do that. It can shrink it though.
Yup. If it's pseudo-gynecomastia or "puffy nipples" it can greatly reduce the volume. The glandular tissue will still be in tact, and very susceptible to exogenous and endogenous hormones.
You may also want to look into running a little aromasin as well. It should help to lower aromatase enzymes so estrogen doesn't rebound too destructively. Letro is a brute force way of slaughtering estrogen... it's very shitty on your system (particularly your sex drive - it will be completely diminished), but it can usually do the trick in a pinch. If you're between girlfriends I would give it a shot. If you have a steady woman, now is the time to fess up about your AAS usage if you haven't already.
Make sure that you're good at eating out pussy. And I mean this with all sincerity and seriousness. The horror stories on the internet you read are true. A few weeks with a limp member is better than forking out $4000, missing out at the gym and possibly time at work. Just make sure that you research matters beforehand. I don't know if Cialis or Viagra would help with getting it up. Estrogen is pivotal when it comes to libido, maybe a PDE5 inhibitor may aid in lessening the sides, but I wouldn't put my money on it.
Best of luck, bro. I've had some scary encounters with puffy nipples but I've managed to eradicate the problem without resorting to letro. I've come close though, so I feel your pain. Let us know how things go!