I want to learn Jujutsu. How do I go about this? Being well over 40, will I find a trainer?

Where are you at, basically in most areas you merely find a school that teaches it. There are many, and some times a few schools may often many forms, I know my school teaches three different forms

Many schools in this form prefer adults, and you normally will find being over 40 your physcial shape will, It is a full contact sport, so pains and sore musles will be expected.

Have you merely googled your city for it ?

This is ( in my opinion ) one of, if not the best place to learn this art. If they don't have a center close to you, I would still contact them, to see if they know of a teacher in your area.

http://www.gracieacademy.com/