yeah :O
Well, before we even touch topaz, we start with bubble cleaning, redrawing, and leveling.
(not in that order)
First off, do you see the colour difference between where you erased text, and the rest of the page?
You fix that by leveling that page (Image > Adjustments > Levels)OR (CTRL+L)
white goes to the left to make it more white.
Black goes right to make it black.
If you're a complete beginner, I'd suggest reading some tutorials(before touching topaz):
http://senbonzakura.kageyoshi.net/http://sakurahana.com/forum/studio-gallery/4801-manga-cleaning-tutorial-bakas.htmlThere's lots of resources out there. Speed cleaning(with topaz, requires topaz denoise, and topaz clean at the bare minimum) requires tons of time to play with the filters, getting used to what they do, know when to use them, what order to use them. Speed scans, though named "SPEED scans", take a lot more practice compared to normal cleaning in order to achieve fast, good results.
Oh and topaz is usually only used on magazine raws, or really bad tank raws.
I'm about to head off to bed, so I'll catch you later.