I've changed photos to a sepia color, but not in Photoshop like I did with this picture. I just followed these instructions I found online tonight:
Click the button at the bottom of the layers palette that looks like a circle half-white and half-black. Select Hue/Saturation. When the dialog box comes up, check the Colorize check box in the bottom-right. Change the hue to a yellow-reddish color and pull down the saturation. Lighten it a little, as many older pictures don’t reach true black. When your image looks good to you, hit Okay.
It was very easy to do! I know there are many programs out there where you can just click one button, but this is a good way to do it in Photoshop :-)
There are so many ways to learn about photography online. An RSS feed I get every day is from the Digital Photography School. I've learned a lot—reading something almost daily from them. I highly recommend checking them out—they're a great resource for budding photographers!