Start with Inside a Wind Turbine: How It Really Works (12 min, First Gear Animations), then How Wind Turbine Technicians Risk Their Lives to Keep Blades Spinning (10 min, Business Insider). All 14 lessons here are free, from the teachers' own official uploads. You'll need climbing harness (practice), digital multimeter, torque wrench (about $180 of kit). The book to keep beside you: Wind Energy Basics by Paul Gipe.
What you'll need
Climbing harness (practice): Get used to working at height.
Digital multimeter: Electrical faults are half the job.