it depends... is it a flex line or the hard line? Flex lines should be fairly cheap and easy to replace. If it is the hard line that attaches to the frame rail then it would be more expensive... it takes more labor to get that line out and replaced.
Based on your description of the location, I'm assuming you blew the hard line. If it were the flex line then it would be leaking at the wheel.
Something like this is fairly straight-forward. You might want to check with some smaller brake shops and compare prices if cost is really important.
2012 XLT SuperCrew
6.5' Bed, Race Red, Ecoboost, Max Tow