drive repair tips?

I used to work with some engineers when they were designing the DMA Systems removeable HD. When I saw a HD being run on the bench without the cover, I asked about the clean room. The answer was that for what they were doing, the disk would run fine but they did not smoke around the drives nor stir up copius amounts of dust. Being the curious type, I took a drive cover off and ran it for at least a week or so without problems in a somewhat unclean environment. I *think* putting the cover back on would move the air through the internal filter and clean things up again. No idea on the bearing lubricant; most of the bearings I've seen were sealed. Something in the back of my mind says that removing the platters will disturb the relationship of the platters and may result in having to do a low level format. Others here (hopefully) have more and better information about this.