Hello, Euronymous, nice to meet you [img]smile.gif[/img] .
For starters, you need
Near Infinity. It is viewer/editor that does many nice things. It covers all the files Infinity Engine uses.
Then, you need
IEEP. It s primary use are item and spell creating.
Winbiff is optional (extracts existing items from the game), Near Infinity does it better.
Infinity Explorer (is not editor, only viewer) is nice, it can show some things nicer than NI, try them both.
BAMWorkshop is essential if you want to edit item icons (bam files).