I found the Washington Mediation Association. Their webpage lists assorted classes in basic mediation training and other more advanced opportunities. If you want to be certified, you take a basic class (40 to 50 hours in class, as I recall). After that you need at least 24 hours of approved supervised mediation through an approved practicum program or with an approved mentor, plus at least 36 hours of additional mediation.
Mediation training sounds exciting and also scary. I'm an analyst by profession, and mediation is different. It means I'll need to open up my mind and be willing to learn and grow. Even if I just take the training and never use it working for the courts, I'll have it available to use in my life and any other work I might do.
I want to be pretty busy when I first stop working. So I'm thinking I'll take the basic class in late summer or early fall, right after I spend a few weeks sleeping as late as I want in the morning!