I just went through this procedure to make some decals.
First off trying to print with an ink jet is a pain .... much pain. If you don't have access to a lazer, go to a local printing company and have them do it for you. It will save you a lot of grief.
Building your graphic on the computer works great. Save them in the size that you want and bring the disk to that printer I was talking about.
Finally the paper .... I had the choice between using a clear decal paper or one that has a white background. I chose clear and shouldhave went with white. There is lots of colour leeding through a light tone if you are puttingon a dark background so go with the white if you can, it may make it a little easier.
Happy Modelling and God Bless
Robert