They'll probably shut the plant down, and have 500 workers come in to replace everything that needs to be replaced, and then power it up again within a few days, and let it run for another 6 months or so.
Everything will be planned on workplans, and most won't require specialist knowledge... Eg. "Replace pump 205 in building C with this pump. Required skills people: 2x plumber, 2x electrician".