1. For the Ford 4500 with the hydraulic package, the owner's manual says to drain the hydraulic fluid prior to changing the filter. Is this really necessary? Will I lose that much fluid just pulling the filter out the top, or is there some other reason for this direction? 2. The manual has a section called "POWER STEERING RESERVOIR (EXCEPT FORD 4500)". However, there is no section for the 4500! Moreover, the picture appears to be exactly what I have. What am I missing?