I did it in a big project it took a couple days, really wasn't that big a deal, and legacy JavaScript still goes through webpack and works unmodified, then a couple weeks to iron out any kinks in the CI scripts (but was still developing during this time)
A couple days sounds about right and jives with my own experiences, but I feel like "do this in 5 seconds" is pretty misleading, especially for someone who may have never used webpack before. It's absolutely worth the effort, but I wouldn't want someone to be discouraged had they expected a "5 second" solution but then realized it's not quite that simple.
