The parts, parts, parts trick: You might be told you need new rollers, cables, drums, bearings, etc., when you don't, or at highly inflated prices. Good questions to ask when first calling for service include, "How do I know you will only charge me for the parts I actually need?", and "If you don't have all the parts I need, what will you charge me to come back?"
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.
The two set-screws in the winding cones have a 3/8-inch square head, which fits a 3/8-inch open-end wrench or 8-point socket, or a 7/16-inch 12-point socket or 12-point closed-end wrench. I carried an extra wrench in my pocket while winding, since I didn't want to be holding a wound spring that I couldn't set because I had dropped the wrench (although one could rest the winding rod against the door in this case while picking up a dropped tool).
The usually recommended rule for a door being properly balanced is that it should lift "easily" through all its travel. The door may also remain stationary if let go somewhere around the middle of the travel, but a smoothly rolling door many not show this behavior (while a sticky track will!), so easy travel is the only reliable test for proper balance. A difficult door may be due to stiff bearings or rollers in the mechanism, tracks out of alignment, etc., not necessarily the torsion spring adjustment.
If your garage door is opening slowly or making a lot of noise, the problem may not be your opener. So before you buy a new one, check for broken or wobbly rollers and brackets. But don’t replace the bottom roller bracket yourself—the cable attached to it is under extreme tension. You’ll need to call a pro. If you’re replacing the rollers, get nylon rollers. They operate quieter than steel rollers and cost only a few bucks more. Next, check the torsion spring (mounted on the header above the door opening) to see if it’s broken. When one breaks, you’ll see a gap in the coils. You’ll need a pro to replace a broken spring.