One might stack lumber or arrange some other low platform for a steady footing, instead of the ladder. The aluminum ladder shown here is the splendid 16-foot Krause Multimatic, which carries a Type 1A Industrial rating (300 pound working load); I highly recommend it. However, product liability apparently forced this company into bankruptcy in September 2000 and the company ceased operations in June 2001; see http://www.krauseladders.com (this Web site went dead sometime in mid-2002). The world is a dangerous place.
Once the springs are relaxed and loose on the torsion shaft, the lift drums lose their tension on the lift cable, and the cable comes loose. The end of the cable is terminated by a press sleeve, which locks into a ramp on the drum. Different drum styles have a bolt or other method to fix the cable end to the drum. These steel cables are springy and won't stay in place without tension. If my pre-inspection had showed that these cables were worn or frayed, then I would have ordered proper replacements ahead of time from the spring distributor, since this is the opportunity to replace them. Standard hardware-store cable and fittings are not appropriate.
You might be thinking: Aha! Why don't we lift the door, clamp it in place, and install the springs while they are thus safely unwound, rather than deal with all that accumulation of hazardous torque? The answer: At the top-of-travel, the unwound springs are not fully relaxed; they are still clamped to the torsion shaft with a significant stretch along the shaft axis, plus about a half-turn to keep the door snug at the top. This extra length amounts to the stacking of extra turns that accumulate from winding, also termed "spring growth" in the business. In my case this is about 7 turns of 0.2253 wire, or about 2 inches. Stretching the spring that much and clamping it with a half-turn or so of twist is not feasible.
Now 13 pounds of force must be respected when backed by many hundreds of foot-pounds of stored energy, waiting to be released. Holding this torque is equivalent to stalling a 3 horsepower DC motor. But holding and turning these handles does not require extraordinary human strength. Note that this maximum tangential force depends only on the weight of the door, and the radius of the drums, and is divided by the number of springs (some designs have only one longer spring, as mine did originally, instead of two shorter ones). Higher or lower lift distances imply more or less turns to wind the spring (and thus a different spring geometry), but not more force on each turn.
Spending your whole weekend setting up a new garage door opener is not on the top of most peoples list. This opener is easy to install for most levels of DIYers and it provides a quiet and reliable open and close. This has 3/4 HPc DC chain features and the powerhead can open 12" in a second. It has a wireless remote and Intellicode 2 security to prevent people from breaking into your home.
Uncentered center bearing plate: The center bearing plate need not actually be in the center. It doesn't much matter where it is, since the purpose of the bracket is to anchor the spring ends. This anchoring must be secure, since all the torsion is held together at that point. On a stud-framed wall, this bracket may be placed over the stud closest to the center rather than exactly at the center of the door opening.
You might genuinely need some extra parts when you thought you simply needed a broken spring replaced, and a good serviceman will perform a simple inspection to identify such parts. Nor is it unreasonable for a business to charge separately for a service call versus repair work actually performed. But the best protection for you as a buyer, being somewhat at the mercy of whomever you decide to bring on site, is to understand what is being done, and ask intelligently for a clear explanation or demonstration of why extra parts are required.