Dave,
I drive a lifted Jeep TJ daily and it has a hydraulic throwout bearing assembly stock. Works smooth as silk, and have not had any problems after 72000 miles. It is a sealed system from the clutch master cylinder into the bellhousing area to the TO bearing unit. I plan to install a new TO bearing when it is time to replace the clutch, which is probably coming in the not too distant future. I can find a service manual section on it if it will help with anything you are looking for.