The Prevost Owner's and Maintenance Manuals call for Fan Gearbox oil and Power Steering filter replacement every 50K miles or every year which ever comes first. For some reason this has never been recommended to me during a regular Prevost service visit which is one of many reasons Prevost no longer services our bus. Would appreciate any "tips & tricks" in accomplishing same.

Should the fan gearbox be purged of oil by rotating? Is it likely that air would be introduced to the steering system when replacing the filter requiring a bleeding procedure? Is it a good idea to totally replace steering system fluid from time to time? Appreciate any comments, cautions, etc.