I sometimes use the Territory Realignment Tool to replace a field's contents in Goldmine. Typically, this is because a Salesperson has left and a new one has come on board. I need the Salesperson field for all of their accounts to reflect the new name. I create a group of the affected accounts. Then I go to Tools/Data Management/Territory Realignment. I choose my group to only perform TR against this one section of my database. I pick a field like Salesperson and change the value to the new Salesperson's name. Goldmine updates hundreds of records in no time, the manual version of this process used to take me a long time.
It's good to learn that established tools can help like this!