1. I cringe every time I see someone putting a phone into a back pocket - for just the reason you now have. Eventually, the person is going to forget that there's a phone back there and ... crunch!
2. Repair prices vary by location. Ask at a few different shops. (Cheaper isn't always better - see if anyone's had a cellphone repair, where, and how satisfied they were with the service.) The part is about $150 (shop's cost), so it's not going to be a cheap repair.