In my opinion:
If you want to change the name of the characters based on your own translation, you need to at least re-translate the manga from the beginning, but if you use the previous character name from the stopped project, then you just need to translate the untranslated chapters only.
But I suggest to just use the previous name and continue the translation as is, so that you don't need to re-translate the whole manga.
I could do some cleaning tough,
like leveling, cropping, removing bubbles, rotating, etc. with Photoshop CS3, just don't expect me to do it really quick. Maybe 10-30 black-and-white pages per week depending on the quality of the scans