Phone wont install ICS manually or OTA

Just received a nexus S 4g from an ebay store. Phone checks out fine and is activated on sprint. Soon as it started to get data i checked the updates and ICS 4.0.4 was there. I enabled wifi and downloaded it. When i try to install it, it gives an error with status 7. after hours online i tried to install 4.0.3 first and that wont go through either that also produces an error. Im unsure of where to go now and have been checking online for hours and still cant get it figured out. Its currently running android 2.3.7 gingerbread. If anyone could help or needs more info in order to help i will glady respond as soon as i can! Thanks