$4,000 CAD is a hefty price to pay. For a fully tuned KA it shouldn't cost that much. I would expect to pay around $1000 or above.If you just need a replacement KA, swapping to low mileage KA would be the cheaper way to go.
Check out the nissan junk yards for KA's. Shop around and look for the best deals also.
btw, welcome to nico.
My garage:
Nissan 240sx 96' - project car
Honda Accord 95' - daily commuter
FS: S14 exhaust manifold - $50 shipped