How will they pay for that technology they need to import when the oil ends? They'd need to barter something for something else.

How will any oil-dependent finances deal with the end of oil? By saving and diversifying. Norway's got the savings down good, and in a few decades they should start thinking about diversifying. Until then, they're in a great position because they didn't spend all their oil money on weapons and instead put it into savings for their people.