Since I couldn't find any help on this I thought I would post some info. on how to replace/repair your Playstation 2 headset.
Here's what I did:
(http://img515.imageshack.us/img515/2366/20030101ps2hs00015ey.jpg)
Basically I wanted to use a more comfortable headset than the "standard" PS2 headset.
You just need the PS2 headset's USB box and circuit board.
(http://img515.imageshack.us/img515/2458/20030101ps2hs00029il.jpg)
Here's where to solder the "new" headset's wires:
(http://img515.imageshack.us/img515/8895/20030101ps2hs00034nm.jpg)
And there you go, you could also substitute powered (amplified) speakers instead of headphones and use a seperate mic.
Hope it helps!