If they have the cable retainer is on right they are not a big deal.
No cable spring retainer and I won;t even look at working on one.
Yep. That's for the ones with the large coil springs that run parallel to the track. It's what I have in my old garage. It's supposed to keep the spring in place and let it snap in one plane if it breaks.
The ones with the spring across the door opening have a 4-star device on the spring shaft, and you have to use pry-levers to turn it. Put one in, give it a quarter or half turn, put in another on, back off a bit, remove the first one, move it to the next hole in the star, repeat. If you miss, or the lever pulls out of the star.... WHACK! At best, it'll knock you silly and only break your jaw. At worst... yikes! Knock you off the ladder where all kinds of bad things can happen.
The new ones have the spring across the door opening also. I've installed a few of them. Pretty easy. As I recall, there's a paint stripe across the un-tensioned spring. There's a drill-drive gear on the end. Following instructions (a gift many of us do not have

) you start winding the spring with the drill until so many revolutions of the end of the stripe occur. How many revs is based on the size of the door, spring, etc. When you hit that number of revolutions, you stop. That's about it.
If the spring breaks on either of the latter of the two, it should (should) remain on the shaft, and if it breaks on the first example, it should (should) remain on the safety cables.
Nothing to fear. Just respect. Kinda like lighting.
