This. It's an excellent summary. The essence is to remove it while the door is fully open and the spring is relaxed, then use a pair of 2x4's (one on each side) or step ladder as a safety to keep the door from crashing down.

The current best- practice is to run a steel cable through the center of the spring in case it breaks. If yours doesn't have that, do it to both sides while you are doing this. I am not talking about the normal tension cable that lifts the garage door - it is an extra cable going through the center of the spring that remains slack, and is intended to keep the parts of the spring from flying away if the spring breaks. https://www.amazon.com/scottchen-PRO-Extension-Springs-Galvanized/dp/B09JKDDRHT