If you're talking about the touch screen then you can get a replacement for under £10 on amazon but don't risk replacing it yourself, take it to your closest game shop. If it is something like...
Depends on store, but usually $188 to $200.
about $110 to $120
with me i had to go to have it repaired. and where i went cost about £10 so dont completely worry :)
like $20.00