I have done hundreds of WI talks, mostly on my truck driving work, and lately on my frugal living/brilliant life on a pension. I have three to do in July. I remember the first one, I spent ages making notes, then condensing it down into prompt cards. An audience of about 100 in a village hall in Derbyshire, scary. I soon ditched the cards, I knew my subject and didn't need them. I found it easier to ad lib off the top of my head. I had 20 photographs of my work made into slides, and gave brief details about each job.
What they want is entertaining, not all the technical details, no need to go too deeply into it. Tell them stories, talk to them like you are having a chat with a friend. Many times I have been told I was the best speaker they have ever had. They laughed until they nearly cried, and went home in a happy mood.
In my experience they never paid very much, I only got enough to cover my expenses. I didn't and still don't do it as a job, it's a hobby which I enjoy. Once you start doing talks for them your name will get passed around and you will get more bookings. They usually do a programme for a whole year, so sometimes it's a long time from the phone call to doing the actual talk. One of those I am doing next month was booked over a year ago.
Good luck with it, you don't have to be word perfect. You get about 40 minutes, then questions after.
Ilona