https://www.naa.edu/soldering-tips-for-beginners/
9 Essential Electronics Soldering Tips and Tricks for Beginners
https://rubber-grommet.com
Type D Rubber Grommets
https://www.powerprobe.com
Power Probe Testers and Multi-meters
https://www.autozone.com/diy/repair-guides/wiring-diagrams
Vehicle Schematics
(or use your favorite search engine)