YouTube is great for an overview, but random YouTubers make mistakes. They might say "use a 12mm socket" when the manual says 14mm, stripping your bolt. Always verify with the written manual.
Do not gamble with free, virus-ridden scans. Spend $20–$50 on a legitimate PDF from Cyclepedia or your local Kawasaki dealer. Load it onto a tablet. Get your hands greasy. And ride with the confidence that you can fix anything that breaks. Kawasaki Klx 150 Service Manual Pdf
Use the manual as your bible, but supplement it with owner forums (like ThumperTalk or KLXClub). For example, the manual says to use special tool #57001-1567 to remove the flywheel, but a forum user will tell you a standard harmonic balancer puller works just fine. YouTube is great for an overview, but random