The Well-Trained Mind is published by WW Norton. They do not have a separate booklet or webpage which contains just the revisions. The revisions are corrections, but rather represent new work by the author to find the best and most up-to-date resources available. The basic "how-to homeschool" information is the same.
The new resource recommendations are extensive. If you wish to buy the latest edition, you can find it here: https://welltrainedmind.com/the-well-trained-mind-extended-guide/ . This page also points to curriculum recommendations that were not included in the latest edition