The oil in the booster usually comes from a bad vacuum pump, if it is dirty oil and a film will not hurt you..if more just wipe it out and spray with brake cleaner and wipe...their is no easy way to remove the booster...you need to remove the master cylinder and then get inside the car to remove the nuts from the 4 booster bolts...But uaually the booster causes a hard brake condition..the brake pedal will be very hard to activate...it might just be the seal between master cylinder and the booster..check vacuum at end of hose where it goes into booster...Jim

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James A. Harris