Are Nissan X-Trail spare parts available at maintenance centers or i will have to buy it from outside, and how are the prices?

you can find them at the dealership and independent importers. The prices are moderate—not too cheap but not too expensive either.

The original spare parts were a bit expensive, but you can find imported used parts at lower prices. The issue is that some parts take time to become available, especially major components like the transmission or suspension.