Short answers, pulled from the story.
The United States defeated the Soviet Union 4-3 in the medal round of the 1980 Winter Olympics in Lake Placid, New York, on the 22nd of February 1980. Mike Eruzione scored the winning goal with exactly 10 minutes remaining in the third period.
Herb Brooks coached the 1980 U.S. Olympic hockey team. He held tryouts in Colorado Springs in the summer of 1979, selecting 20 players from a pool of 68 through a process that included a 300-question psychological test. Brooks died in a car crash near Forest Lake, Minnesota on the 11th of August 2003, at the age of 66.
Al Michaels, calling the game on ABC alongside Ken Dryden, delivered the famous line: "Do you believe in miracles? YES!" in the final seconds of the U.S. victory over the Soviet Union. Michaels was the only member of ABC's broadcast team who had previously called ice hockey, having done so at the 1972 Winter Olympics in Sapporo.
No. The 1980 medal round was a round-robin format, not single elimination, so defeating the Soviet Union did not guarantee the gold medal. The U.S. secured gold two days later on the 24th of February 1980, by defeating Finland 4-2 in their final game.
Viktor Tikhonov replaced Tretiak with backup goaltender Vladimir Myshkin immediately after Mark Johnson scored with one second left in the first period, tying the game 2-2. Tikhonov later identified this as "the turning point of the game" and called it "the biggest mistake of my career."
Thirteen of the 20 players on the 1980 U.S. Olympic roster eventually played in the NHL. Five of them played more than 500 NHL games, and three, Neal Broten, Mike Ramsey, and Dave Christian, each played more than 1,000 NHL games.