Replacing both is a good idea as far as preventative maintenance goes. The filter should be some sort of "spin-on" filter on the return side of the hydraulic system. As far as how o drain the system, I would say to remove the lower / supply hose going to the hydraulic pump; of course that would depend on what your hydraulic tank looks like / how it is incorporated into your bobcat. (A picture of your machine would help us too, though. That way we can get a picture of what you are facing.) Once the tank is empty, I would top it off with #46 weight hydraulic fluid. Then let it run for 15 seconds, or until you hear the pump whine, then turn it off & check the level again. Top it off as needed, after operating the bucket lift / tilt a few times. I hope that is helpful.
