Looboss,

The amount of what you can do in Photoshop is almost limitless...

...but so will be the time you spend fixing it.

In my opinion, your time would be best spent drawing a matte to cut your model out, using a path. Paths are really good because you can reuse them and go back to them if you make a mess of your matte at any point.

Here's a very quick how to:

Window Menu > Show Paths.
Path Floater > Create New Path
Tool Floater > Pen

Quickly draw a Path around your model. Then use the White Arrow (Hidden behind Black Arrow) and the Flying V to adjust the shape of your path to fit the model exactly. You can zoom right in to do this.

Right click on the Path Picon and select Make Selection. Keep Anti-Alias selected and try out different amounts of feather (I use 1 or 2 pixels). A strippey sting will appear to indicate your mask.

On the Layers Floater, make sure your layer isn't pad-locked. At the bottom click the Icon that looks like a Circle in a rectangle (Add Layer Mask). This will cut you model out!

Now you can add a plain white background or even add a copy of the original photo below and colour correct it until the background is the way you'd like.