Despite the above precautions when putting a new filter on my car, I still ended up twisting the hard line from the tank. The fitting on the line was basically frozen, and despite the fact that I used penetrant on it (and tapped it with a wrench to get it to set), it still was seized.
If you don't get it off without mangling the hard line, don't panic. I used a small tubing cutter and cut of a ~4" section, and spliced in a fuel filter with a nipple on the end instead of the welded nut (thanks salvagev6!). I double clamped it, and bent the cut end to prevent any unnecessary bends that may restrict flow.
Good luck.
S.