how much money to replace just the screen?

Apple does not repair iPads, but will replace the entire iPad for a flat fee. See the Repair Pricing section here:

http://www.apple.com/support/ipad/service/faq/

There are independent iPad repair services that may be able to replace the screen for less. Do a web search for "ipad repair". You can also look for parts and instructions and do the repair yourself. Note, though, that if you elect to have the iPad serviced by an unauthorized shop or perform your own repair, you will get no further support from Apple.

Regards.

The standard 1-year Apple Care warranty only covers defects in materials and workmanship, not damage due to accidents.

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.

Out-of-Warranty Service

If you own an iPad that is ineligible for warranty service but is eligible for Out-of-Warranty (OOW) Service, Apple will replace (Apple doesn't repair) 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. (The replacement will most likely be a refurbished iPad in a brown box, however, it has a new screen, back and battery.)

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

http://www.apple.com/retail/geniusbar/

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

http://www.ifixyouri.com/16-ipad-repairs

RepairZoom iPad Repair

http://www.repairzoom.com/ipad-repair.html

Mission Repair

http://www.missionrepair.com/Apple_iPad_Repair_Services_s/431.htm

iGadgetResQ

http://www.igadgetresq.com/ipad-repair/

 Cheers, Tom 😉