As Glen and Guy have pointed out, the hydroboost pump provides the power for both the steering and the power brakes. Replacements can be had from Mills, RockAuto.com or any aftermarket auto parts supplier. I bought a rebuilt pump with a lifetime warrantee from AutoZone for about $60. New pumps are pretty expensive. Either way it's a special order part and will take the better part of a week to get one.
Replacing the pump is a real PITA. Here is a link to my saga that began with a water pump failure and ended with the replacement of my pump (http://www.airforums.com/forum...ght=hydroboost
If you plan to do this youself, feel free to PM me as there are some tricks. In all honestly, this is one that I would gladly pay a professional mechanic to do for me in the future.