They shouldn't give you a hard time because of the volume button. That's completely unrelated. If the screen isn't working and there's no obvious damage such as cracking/water then you should be able to invoke the manufacturer's warranty.
Are you running TouchFlo? If so, use the dpad to get to the contacts tab and try fiddling around with the buttons so you select a contact to send a text message.
BTW, here's a picture of the warranty info you should bring up (I meant to highlight display instead of keyboard):
