#1 First off, I doubt the software is legal, it is already against the user license to resell the software. If you want to get the software legitimately for a low price I suggest buying Photoshop at student pricing, if your not a student, then maybe you have a friend that is…
#2 Photoshop CS4 is one of the biggest releases for the 3D industry, for photo editors, and painters, there are some nice improvements but nothing huge, but for 3D artists the improvements are pretty big.
Photoshop CS3 saw an intro to 3D work, with the Vanishing Point feature, which allows you to project an image onto a 3D surface. In CS4 it is completely redesigned with many more functions and CS4 now has the capability to paint directly onto 3D objects. A HUGE plus to 3D artists. And make sure you purchase CS4 Extended, because CS4 Standard does not have these capabilities. CS4 Extended also has the ability to composite 3D with 2D imaging as well.
Hope this Helps,
-Austin