90Q brake problem

["Vlajko Jokic" <vlajko.jokic@sympatico.ca>]

An excessive pedal effort is required to stop my 1988 90Q. I think that power
brake booster is gone. If the pedal is depress while the engine is running, and
then the engine is stopped, the pedal rise instantly, pushing my foot up. Also,
when engine is stopped (without having brake pedal depressed while running),
and then the brake applied, no signs of booster airtightness. That means,  
pedal feels too hard  as the engine was not running for hours.  Finally, if the
pedal is strongly depressed while engine is running, I can hear air leak noise
coming from the place where pedal is attached to the booster.

Does anybody know is some seal replaceable inside the booster, or I have to
replace whole unit? Some information about price would be very helpful, as
well.  Is this unit maybe the same as one on Golf/Jetta?

Regards,

Vlajko Jokic
Canada

88 90Q