I don't think anyone has tried it but I'll try my best to help
Short answer is yes the bumper will fit in place of the GT base. Might need to drill a few holes in the wheel liner but I doubt it would be anything serious.
The exhaust would need to be custom made, spacing might be a bit tricky since the base model has cross beam suspension that can get in the way
If possible I would try to find another N-line locally and park your car beside it and see any wheel liner/plastic/fasteners that would be different from yours. Your best bet would be to find a wrecked N-line and get the parts off that.
Whether it's worth the hassle/money is for you to decide