1. Ok first of all Here is the link for the tools.
2. Get DatMan! Light v1.2 or Fallout 2 DAT Explorer v1.42, your choice
3.Unpack your master.dat (from the cd, or if you installed humangous installation you can extract from the master.dat in your fallout directory.
4.Get FIME or FIC (In the fallout1 section) or the mapper and start editing, remember READ THE README's they will give you all the answers you need...