Anyone w/ 1990 FSM...vacuum leak from brake pedal at firewall

[DamnedButDetermined]

this is a picture of were the brake booster and brake pedal attaches (not an actual 240sx)


Now if you get on your knees and look at the firewall: There is a threaded rod that attaches to the pedal and goes through the firewall. There is a black rubber boot/protector/seal i don't know what is is, but when i push in the brake pedal i can feel air getting sucked into the firewall.

Now if you look at the picture... at top of the brake booster, there is a vacuum hose attachment and a hose that goes all the way back to the engine. So basically the booster needs to have really good seals in order to keep a vacuum and make the booster work properly.

My questions are as follows...

Do think i need to replace the entire brake booster, or just a seal?

If I can replace just a seal, what part number would it be? I don't have a service manual nor a diagram of the braking system so i don't know how many seals there are that could be comprimised(sp?)

What is the procedure for taking off the brake booster? Do i need to disconnect things inside of the car or will taking off the master cylinder and unbolting whatever there is attached to the booster be all that is required to remove it?

Would there be any benefit to buying a larger or smaller boster from another nissan to improve braking? I do know that a larger one will make puching the brakes easier, and a smaller one will make it harder. Is there any benefit to be gained IE: more pedal feel, more precise braking, ect. If there is any benefit, which vehicle should i get one for? 300zx, maxima, altima, Q45, J30???

Thanks for your time,
-DbD-