Haha when you dye your hair, it will grow out its natural color. There's no way to reverse grey hair.

As for wrinkles, the only semi-permanent reversal is plastic surgery.

Putting almond oil under your eyes reverses panda eyes. Your best fight against premature aging is going to be drinking 1.5 gallons of water a day and taking lots of vitamin C. I take about 1,500 mgs a day for that purpose. You can google it and there are studies done that show people drinking a gallon+ a day and reverse wrinkles. It is actually pretty hard to drink that much unless you are able to pee 500 times a day...

This shampoo claims to restore grey hair http://www.peterlamas.com/h_chshampoo.php I hear they are working on a pill that stops grey hair growth.

also any suggestion for vitamins/ lifestyle to adopt in order to prevent premature aging?

Experiment on yourself.

Increase your intake of water rich foods and increase your intake of good water (filtered water with a pinch of sea salt or a bit of lime juice). Moisturize yourself from within.

Eat plenty of beneficial fats to preserve your suppleness/juiciness- avocados, coconut cream, hemp seeds

Rest more, this includes mental rest (silence or meditation).

Reduce your stress. Find ways to make life easier for yourself.

Do your best to reduce your intake of sweet foods (that includes fruits like bananas).

And, most importantly, find ways to be happy.

For gray hair, I read that seaweeds are helpful.

Exercising daily is also helpful in maintaining a vibrant appearance.

All of my suggestions are based on observing how others who remain 'youthful' live their lives.