how much to replace or repair Ipad metal case?

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.

Apple will provide a replacement iPad for:

Make a Genius Bar Reservation

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

You can get the iPad repaired at 3rd party repair sources for less $, however, the 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 😉

If you make a Genius Bar appointment at your nearest Apple Store you can do an out-of-warranty replacement for $250 USD. But if it is working why not just put a case on it?

If it's a matter of appearance, don't look at it!