Photo Paint - colours

I need some help with Photopaint as I'm a anovice user!

Basically I want to take a picture of a man wearing a t-shirt and be able to change the colour of the t-shirt, while still keeping it looking like a real t-shirt (eg wrinkles, shading) rather than a t-shirt shaped block of colour, which is all I've managed so far.

I sell T-shirts and want to have a standard t-shirt picture which I can change the colour of and add logos to, is this even possible?!