Editing work

I have been trying to slog through all the editing work that is needed on the novel I wrote during the National Novel writing month challenges from 2006 and 2007. I have actually been working on the edits for about a month now and feel I am almost done. As I received an email detailing how I could get a proof copy of my novel if I upload it to one of the printing sites, I am trying to hurry against that deadline to get the novel edited, uploaded and ready to go. I have finished most of the editing and have had a few readers also help with the editing. I have realized that there are a few words I should read up on how to use correctly as I seem to use them incorrectly with extreme frequency. My biggest ones are 'then' and than'. I seem to get dinged on that almost every single time I use the word, that now I am unsure how to use them. I might be able to simply avoid using them but not sure I want to have to be that extreme. I am still waiting for some final edits back from my father.