Need Help With MySQL + PHP Queries for Database With 31M Rows (ASAP)

Hi. I need some help for the next 4-5 hours. I'm trying to clean up a big "master" table with 31 million rows. It has Categories in it that are repeated for some items/rows, so we need to put all the unique Categories in a new table, then add 24 character alphanumeric codes to each of them, which we will also put in the "master" table to bind the Categories to it. I also need to remove some columns from the "master" table that aren't needed - from my understanding it may be quickest to copy the table to a new table - only copying the 3-4 needed columns, right? I have a VPS, but could probably also share the .sql table with you, so you can clean it up on your own then send back to me. I need this ASAP.