Replacing a fan-belt:
In the old days (ok, I'm beginning to date myself) the fan-belt operated . . . well. . . the fan. Today the fan-belt operates the: water pump, power steering, air-conditioner, and alternator.
In the past you were told (by the old-timers) that if you broke a fan-belt out in the middle of nowhere you could fix it by snuggly tying a ladies stocking in place (all guys were G.I.'s and all G.I.'s carried stockings. . . and chocolate bars).
Step One: remove engine.
Yes, that's right. Well maybe not that literal, but to replace a "serpentine belt" in a Pontiac Bonneville you have to first remove a motor mount. The belt goes so many places and the engine compartment is so packed that the only way they could keep the engine from falling out on to the ground was to put an engine mount through a loop of the fan-belt.