Kathryn, the process is like any other refinishing. You get to a smooth surface, prime and paint. The present condition determines what you will have to do to get to a good surface. You may have to strip the old paint. Probably you will just have to sand. Possibly, you will have problems with rust. In any case, you treat the cabinets the same way, basically, that you prepare a car for repainting. The better the prep work, the better the work will look.
One thing to consider is that the paint may contain lead. Unless you are 100% sure that they are newer than from 1975, proceed as if the paint contains lead.
If you know a good auto body painter, he may be able to guide you through this. The specifics can vary with the condition quite a bit. In any case, I feel that these cabinets should be spray painted with a gun. That's the way they were originally done.