You shouldn't be thinking in terms of sharpening, or cleaning up the raster image text. Recreate the text using a Type layer matching the font, and using Free Transform to match perspective etc. Blank the original, and it's job done. If the result is too clean to look real, then distress the text to suit the image.
I see you are using CS6. You would not believe the difference between that and current versions. The beta version of Illustrator can scan text in an image. Match the font, and perspective, and change it to live text. Even without using Photoshop, Illustrator or other image apps, there are any number of apps that can do OCR (Optical Character Recognition) and turn raster text to live text. Acrobat being an obvious example.
If you want more help, show us a full res version of the entire image, and describe what you would like to achieve, and you'll get lots of help. That's 100% certainty, because we love doing shite like that. 🙂
... View more