you dont need to take off the big nut. also do you have your parking brake off?
and if it still doesnt come off with the brake off then use 2, 6mm bolts and screw them in to the threaded holes in the rotor to push them off.
you need to be a little more descriptive about what is happenening.
but my guess would be your door latch. you prabably need to take the door pannel off and grease up the latch from the inside or just change it.
the ps system uses regular ATF.
the valve your talking about is probably only available from the dealer. if you look at your pump there should be 2 vaccum lines that go from under(?) the pump to some vaccum tubes on the engine. if you trace those lines to the pump you will find the valve. that valve controlls the steering effort according to speed.
if you fill your car with 16 gallons what is the difference between regular and premium? about $3.20. your going to put in fuel that was not designed for the engine putting it at risk for premature failure just to save an amount of money that cant even buy a #1 at Mc Donalds. sell your car and get a geo metro.
like jibbby said it is very noisy but so is most every clutch type limited slip. if you want a quiet lsd you should probably stick with the supra torsen lsd
sorry it was kaaz but here's a random link if you do decide to go this route you may need to call and ask for the right application
http://www.frsport.com/KAAZ-DAT3020-2-WAY-...-96_p_8632.html