Well, before I start telling you stuff, I need to know what scans you're working on so we don't make duplicates. The people I know working on this right now is LukewarmHoliday, who's working on pages 69 through 86, and me (I've done pages 1 through 12 and page 68).
As for the other question, this topic may help:
http://lacrimacastle.net/forum/index.php?showtopic=3153It's a tutorial on how I clean the scans, but it was written with GIMP in mind. I don't remember if Photoshop has similar features on it or not.