The 30-pin connector on the iPad is not really designed to allow for the use of USB keyboards. It's rare if someone gets one to work. However, a lot of people have had great success with Bluetooth keyboards. Perhaps you could look into getting one of those?
And, there is no way to access the main file system on a stock iPad. They are not designed, by Apple, for that type of access. The only way to access the full system and its files is to jail break it.
Marilyn