As far as software you will need any program that can save as vector graphics, that way they are 100% scaleable and will print exactly as you have made them with no distortions etc.
I use Serif Draw and Page plus as they can do vector and are easy to use, most of the Serif range is available in download as well as buy on disk. If you go to their web site they have all the detail. You can get older versions of the software from download sites etc and often on computer magazine cover disks.
They are somewhat cheaper than the Adobe range of products. I use them for printing decals for RC cars and Replacement decals that I messed up.