can someone explain to me how to lift this on paint.net?
sorry if its too big

http://i173.photobucket.com/albums/w45/stevblev/DSCN1771.jpg

You would have to "select" (outline) the entire truck body/frame and lift it up. Then you could paste some bigger tires/wheels.

Here's a quick chop/animation I just did. Once you lift the body and get paste bigger tires on, then its just a matter of filling in all the empty spaces and making it look good.

http://img373.imageshack.us/img373/1197/stevotruckht0.gif

Sometimes it is easy to do what Matt just did with the body and just find a lifted chassis (with wheels) to stick it on.

Lifting is a LOT harder than lowering for that very reason.

Or, you can simply lower the wheels, which is much simpler than raising the truck. ; )
http://tfdiamond.googlepages.com/pic_stevolifttruck.jpg

Here it is with some meat. I didn't take much time to clean it up. But you get the idea.
http://tfdiamond.googlepages.com/pic_stevolifttruck02.jpg

EDIT: Combining consecutive posts.

Here it is with some meat. I didn't take much time to clean it up. But you get the idea.
http://tfdiamond.googlepages.com/pic_stevolifttruck02.jpg

good thinking bout lowerin the wheels, also for future reference, whats the best tool to use when outlining the truck?

Not sure in paint.net but in Photoshop CS3 I use the polygonal lasso and just click my way around the entire vehicle after zooming in 4-5x (400-500%). It is very tedious and time consuming but until someone can show me a better (and just as accurate) way to do that is what I will stick to.