I think my '95 Marquis which has the same engine as yours has a similar hydraulic system. I will be doing what you are planning in a few months. The fluid reservoir/filter on my coach is behind the remote run panel and I will need to remove the air filter assembly it seems for access. I was going to contact Gillig for the correct filter part numbers as they built my chassis. I was planning on draining the reservoir and the cooler, then refilling and add as needed when all air is bled. You could drain and open up the reservoir and see what you have for filters. As Yogi Berra says," you can learn a lot just by looking "