F*** doing things yourself. That's for peasants. I like saving money as much as the next guy but working alone and putting your safety at risk is just stupid.
I have segmented, wooden garage doors that weight at least a few hundred pounds. They're on springs rated at 250lbs each. I decided that I would try to change one of the springs (don't ask, it was long overdue). I really need to change the cable too but I didn't have time for that since it involves removing a bracket and yada, yada.
Anyway, I get the old spring off and it's so heavy that it slips out of my hand and goes crashing into the wall. Well, a tool stand in front of the wall. First mishap. I change one of the pulleys, put the new spring on, go to close the door only to find that the cable is off of the other pulley.
Now it looks like there's not enough slack to rehook the cable. So I have to get out a ratcheting strap binder and hook that between the spring and the railing to take up the slack. This is a 250lb spring remember. I'm not happy about this. Get the cable back on the pulley but now it's off on the other pulley. Reattach the strap binder, retension the spring, get the cable on. Finally everything seems to work.
But at any step I could have slipped up, fallen off the ladder, had the spring get loose and snap back or god knows what else. And let's not forget the couple of times the garage door wasn't connected the to the springs and decided to make a run for it. I'm not doing this shit any more. Plus I almost forgot to retighten the braket that connects the spring to the main support bracket. A pro would probably at least have a checklist not to mention an apprentice or helper.