+1 on the hacksaw. Take some extra blades with you just in case. Been there, done that.
On the roof rails take some heavy fishing line (or a bicycle brake cable since you don't need to worry about damaging the roof) and get it under the front or rear end of the rails and work it back and forth in a sawing motion while pulling it towards you. Should cut through the tape w/o damaging the rails. Just be careful with so you don't catch the edges of the rails. Don't use a screwdriver or anything to pry them off or it will dent them.
If you can get them off w/o damage and pack em up so they don't get killed in shipping I'd take them if they're reasonable cost-wise. Been looking at a set for $130 shipped right now but if you can come in under that I'd take them. Paint condition is no issue, just as long as there isn't cosmetic damage (which happens when people use screwdrivers to pry them loose).
