What type of exercises should I do after the surgery to avoid saggy skin?? Cardio, weights, etc?? And is there any kind of cream or lotion that i can use to tighten skin?

Moisturize (anything petroleum based will do at keeping moisture in), Protein high, massages help, lots of Fluid and exercise. You want as much muscle under the skin as possible. That said, I hope you picked your ancestors well, because genetics seems to be the most important factor.

I was told resistance and weight training help tone the skin/muscle, as well as swimming.

Was told by my doctor to do weights to help tone and not to much cardio and to walk

Weight train, stay hydrated, keep your protein up, use a good moisturizer, and exfoliate your skin.