There are tons of sites that help with Photoshop tutorials. Some might be for outdated versions of Photoshop, but some of them can still be very useful.
As far as I'm aware, I don't believe there were too many changes from CS2 to CS3. So, if you do have any in depth questions that none of the tutorials cover or cover as much as you like, I can try to help you.
As far as to what you'd like to do, you might want to start by using the magnetic lasso tool to select you and put you in a separate layer from the background. This way, you can play around with the background and not affect you at all.
This site: http://graphicssoft.about.com/od/photoshop...rbps_3aleaf.htm
explains how to use it, even going into to using the Quick Mask tool, which will help get the areas that might be a little more tricky to get.
Once you begin to read this: "Next the selection is inverted (Selection > Invert) and the background is deleted by pressing delete on the keyboard. Make sure your image is on a layer before hitting delete. If the layer palette shows only one layer labeled background, you must promote it to a layer by double clicking on the background in the layers palette."
Ignore it. You don't want to delete the background. Instead, you'll want to copy and then paste it(Note: Make sure that the background has been turned into a layer for this to work. To do this, just double click on the background and a window will come up, just click OK and you should see 'Layer 0'). It'll keep it in the same spot, and yet you will be on a separate layer from the background. Unless of course, you plan on putting something else in place of the background, then you may continue with the tutorial and delete the background.
Now, if you want to manipulate the background, you can use the effects and/or play with the brightness/contrast and/or Hue and Saturation. It obviously depends on what you'd like to do and what look you are trying to achieve.
Brightness/Contrast and Hue and Saturation are both located under Image>Adjustments menus. Make sure that 'preview' is checked so that you can see what it'll look like before you hit OK.
Effects are located under the Filter menu. You can also preview these prior to hitting OK. I usually go to Artistic>Colored Pencil, and another window will pop up, along with other choices. If you click on the colored pencil choice, you can use your arrow keys to move through the choices and see the effect on the left.
If you are looking to delete the background (or you can do this with your background as well) and add some designs or another photo to use as a background, you can always look into scanning in things and maybe using them as filter effects, or using photoshop brushes to create different effects.
If you have a scanner or even a digital camera, you can use anything that might have any texture or design. I also have a folder of textures that you can use if you'd like. I can send them to you if you wish. Either way, you can load any texture, as long as it is saved in the .PSD (Photoshop Document aka Photoshop's native format) format.
Here is a site explaining some more on how to do that: http://www.sketchpad.net/texture1.htm
In short, what it is explaining is once you've taken something you've either scanned or taken a picture of, load it into photoshop quickly save it into a folder and save it as a .PSD file. Then, you go to Filter>Texture>Texturizer and there should be a small arrow next to the texture name box beneath the 'Cancel' button. Click it and it should say 'Load Texture', then click that. Search for the folder where you saved your texture and load it in. Automatically, you can see your texture on your image. You can play with the direction of light, the scaling, relief and if you would like to invert it.
As I also mentioned (I apologize if this seems overwhelming, as I know Photoshop must be new to you, I just want to show you some different things you can use and do in Photoshop. I can explain anything more in depth and create some step by steps for you if you need it), you can use Photoshop brushes. All you have to do is google 'Free Photoshop Brushes" and hundreds of sites will appear and you can go from grunge, floral, trees, stars, etc etc. Those you can download and you will just load them into your brush sets within Photoshop. I believe they will explain that and how to do it, but if not:
Select the Brush tool, go to where you would select your brush and next to the 'Master Diameter' slide, there is an arrow, click that and select Load Brushes. Here is where you will load the brushes and obviously, you can select from there the brush you'd like to use. You can create different effects and looks by using brushes.
You may also want to look into this website: http://www.good-tutorials.com/tutorials/photoshop
Where there is other things you may want to do, including using textures, photo effects, regular effects, etc. Here you can search on your own and explore and it'll help give you some ideas. There is also a basics section where you might want to start if you'd like to get a good handle with Photoshop and become more comfortable with it.
Again, I apologize if this is overwhelming, but I wanted to give you a slight scope with what you can do. If you need anymore help, I, and I'm sure stevealmighty, can assist you if you need any further help. I do hope that I've helped you and that you do have fun exploring and learning Photoshop. Also, I'm going with my own version, CS2, with helping you locate things. If anything isn't as how I showed you here, let me know and I'll help you find it!
Good luck, latino209.