14" hard drive refurbish question (7900A)

I finally got around to putting a new lower platter into my 7900A. Kinda hard to do from underneath, but it's done. Now I'm getting ready to take the lower heads out for thorough cleaning. Before I do, I wanted to ask some advice... When I powered the drive up before, I could hear minor HDI (very slight scraping). Upon inspection it was obviously the lower platter that was missing a track of oxide. The heads had oxide on them but they didn't look all that bad to me. Most of the folks on the list (and a few people I talked to voice) said just replace the lower platter and clean the bottom heads and all would probably be well. Two questions: 1) Everyone said because the lower platter is fixed, there's no concern for alignment, precision, feeler guages, etc. Just unbolt the heads, clean 'em, and bolt 'em back on. No special checks and so forth. Before I unbolt them I wanted to double check and make sure I wasn't about to do anything silly. So - just unbolt, remove, clean, rebolt, and power up? 2) I was thinking (bad sign <grin>)...if the heads contacted the platter enough to scrape off a nice circle of oxide, won't cleaning the heads and replacing the platter accomplish nothing? What I mean is - isn't it very likely that whatever caused them to scrape in the first place won't be fixed by a new lower platter and cleaned heads? What am I missing here? Thanks in advance for the education on 14" hard discs! Jay West