PathLiar
Personally I would not be overly surprised if Oberyn doesn't take the warning to heart. He is too arrogant in his own abilities and will only be more so when they're at his home turf. All those years of grief and bitter hatred for the mountain will probably overflow and he will want to make the man suffer and play with him before the kill. The situation is different from the show, obviously, so he might survive... but I'd be impressed if Oberyn doesn't suffer some grievous or crippling injury before finally slaying the giant, all because he doesn't finish it quick enough. A gouged eye, crushed hand, or some other obvious injury that while not fatal will leave its mark. I don't think it'd fit the overall grimdark theme of GoT if Oberyn manages to actually execute the assassination too flawlessly - even though he probably COULD if he had restraint. He's just too emotional about this one. But we'll see.