The button label can be easily changed by Photoshop (Image Ready). Usually we supply the templates with layered psd file. This file also includes all slices (pieces) of images that formed the template layout.
Once you open the file inside the Photoshop, just change the text for the button and then by using Image Ready (this program is part of Photoshop 5.5 and above) save the image as a Web page.
You also can open the PSD file by Paint Shop Pro 8, but the slices are not visible.
Modifying of the jpg images is not very good idea, because is very slow and result is not fine.
Once again I send you the button's images with "services" label, so just replace them.