I agree, the springs are a doable job, but they are one of the few jobs I am *mega* careful about (another being working in a breaker panel close to live main lugs). It's a very low tech job, but could become extremely dangerous. I use two cut off pieces of rod stock (1/2" I think, 18" long) with the ends chamfered lightly, and keep two 1/4" wrenches handy for the set screws (if I only had one I'd lose it somehow). Stand on a 4' ladder and go slow and careful.
One thing I have found helpful is to paint horizontal stripes on the springs before adjusting them, so that later on you have a reference to work with when re-tensioning everything. Makes it easy to get back to where you started. Springs usually have some sort of factory striping but it's hard to see after some years and it's not always helpful for an already tensioned spring. Also make sure the door doesn't stick for any reason (paint, friction, etc) as that can really trick your tensioning work. I remember doing one door for a neighbor that was sticky the first 1-2 feet and then launched itself with too much force (actually shot back and up and rammed into the stops on the end of the track). We backed off the spring a little, but then had to fix his door gaskets to make it easy enough to raise without sticking.
