It goes against my nature to give up.........

.....but I don't have enough hours in the day to get something done that I committed to. I agreed to review a course for my (part-time?) online employer (I just can't turn down money). But we didn't get the paperwork until last Saturday, and the course review has to be finished by this Friday at noon. We have Open House at my school Thursday night, and I'm on Unit 5.........out of 18. We have to look at every single content page and correct grammar and spelling. Those of you who have read my posts know that I'm a grammar snob, so they surely came to the right person. But I also have to fill out a form documenting every change I make. Every comma I add, every apostrophe, every spelling change. And I have to check every single link and make sure it goes where it's supposed to. And I'm required to check every single quiz, assignment check, and unit test, making sure all the questions are correct in spelling and grammar and that the answer is the correct one. They said course review was supposed to take 10-15 hours, but a unit test alone takes at least an hour to check. Arrrrrrrgggggghhhhhhhh!!!!!! I don't like admitting defeat, but I don't like stressing out either. Oh, and I'm also supposed to be checking my own course's Units 1 and 2 and......oh yeah......actually teaching the courses I'm assigned to teach. Is it wrong of me to go back on my word and say "I can't do this"? Or is it wronger for me to do a half-assed job and still collect the money they pay me?