Not sure what I used, but a 0 or 00 are the most commonly used phillips heads for stuff larger than eyeglass screws and smaller than, say a computer tower. I've gotten to where I don't even choose anymore; those two screwdrivers are at the top of my drawer and I grab one without looking. Granted, in theory you should always have the exact screwdriver for the job (is what I've always been told, anyway), but when it's late at night and no one's looking I just know I get the screws in/out.
I've always appreciated my MDR-V150's. Bear in mind I have much better headphones than those. They get a lot of bad pub here. Bad instrument separation, muddy across the frequency range, lack of detail, worst phones ever. I'm pretty sure I've seen all those comments on head-fi. I've noticed all but the last one to come up in my own experience using these things. But if mine didn't break, though, I'd still be wearing them, even though I've leveled up to headphone collector since joining these forums. And I will fix them.
The pads are more technique than anything, but require patience as well. You hook as much as you can on one side, push or otherwise hold that part on, work a little bit more onto the cup by gently pulling, stretching, and I guess rotating.
What mods are you considering? I dremeled mine so they fold like my 7506 (not nicely though). You could try a driver transplant, recable (I mic'ed mine for iPhone/Blackberry), single side cable. I've thought about putting a hinge in the middle of the headband like the same size Denon portables. I mean, the sucker's in pieces and I'm not doing anything with them, you know?
