Modelling a character is very VERY hard. If you havent modelled anything before, you'll need to get some practice in on other stuff first. I've been modelling for a couple of years now and I am only beginning to think about doing a proper character now. I did lots of making naked chicks at the start (as everyone does?!) but they were all rubbish cos i didnt know what i was doing. So either get really into 3d studio max for a couple of years, or find the .dds texture file for the current soldier model and recolour it, which is a hell of a lot easier and how nearly all of the soldiers you see ingame are done. However, I know next to nothing about how recolours are done, but i imagine someone else will chip in with some info.
And also if your wanting your solider to get into PR then you will need to do a reskin of an existing player model + extra kit gemos ontop since we are now not going to be using any more new player models. There's a topic on it somewhere if you need more info on why you shouldn't model a new player model from scratch.