It depends. I’ve done several vBulletin imports. It’s surprising how different they have all been. It may be that the script will work “out of the box” or it might need customization, depending on how perfect you need things to be, what Add-ons you have used, and any quirks your community might have in how they have used it. Imports pay my mortgage, you can check out Discourse Migration — Literate Computing, LLC which outlines issues you’ll need to consider whether you do it yourself or get someone to do it for you.