Error 1 or -1 (from 2nd link below)
This may indicate a hardware issue with your device. Follow Troubleshooting security software issues, and restore your device on a different known-good computer. If the errors persist on another computer, the device may need service.
Update and restore alert messages on iPhone, iPad, and iPod touch
iOS: Resolving update and restore alert messages
iPad: Unable to update or restore
Are you trying to update your iOS?
If you have an iPad 1, the max iOS is 5.1.1. For newer iPads, the current iOS is 6.0.1. For the iPad Mini the iOS is 6.0.2. The Settings>General>Software Update only appears if you have iOS 5.0 or higher currently installed.
iOS 5: Updating your device to iOS 5 or Later
How to install iOS 6
iOS: How to update your iPhone, iPad, or iPod touch
If you are currently running an iOS lower than 5.0, connect the iPad to the computer, open iTunes. Then select the iPad under the Devices heading on the left, click on the Summary tab and then click on Check for Update.
Tip - If connected to your computer, you may need to disable your firewall and anitvirus software temporarily. Then download and install the iOS update. Be sure and backup your iPad before the iOS update. After you update an iPad (except iPad 1) to iOS 6.x, the next update can be installed via wifi (i.e., not connected to your computer).
Your iPad must be past its warranty date.
Apple's Limited Warranty http://www.apple.com/legal/warranty/ for iPad excludes coverage for damage resulting from accident, disassembly, unauthorized service and unauthorized modifications.
If you own an iPad that is ineligible for warranty service but is eligible for Out-of-Warranty (OOW) Service, Apple will replace your iPad with an iPad that is new or equivalent to new in both performance and reliability for the Out-of-Warranty Service fee listed below.
iPad model Out-of-Warranty Service Fee iPad mini $219 iPad 3rd, 4th generation $299 iPad 2, iPad $249
A $6.95 shipping fee will be added if service is arranged through Apple and requires shipping. All fees are in US dollars and are subject to local tax.
Certain damage is ineligible for out-of-warranty service, including catastrophic damage, such as the device separating into multiple pieces, and inoperability caused by unauthorized modifications. However, an iPad that has failed due to contact with liquid may be eligible for out-of-warranty service. See http://support.apple.com/kb/index?page=servicefaq&geo=United_States&product=ipad
Make a Genius Bar Reservation
You may can get the iPad repaired at 3rd party repair sources for less $, however, any remaining Apple warranty will be voided.
iPad Repair & Screen Replacement Services
RepairZoom iPad Repair