Dealer says my steering assembly has a leak, and requires replacement. That part is expensive $1500!!
Is it possible that this assembly is repairable?
Is there companies that will rebuild them?

I have some time to do research on this; dealer says it will take them 3 months to order the part (it's a US spec car, in Middle East, and the parts are "different")

Regards

 

Here's as good a place as any to start your research:
Steering rack rebuild
Rebuilt G37 steering rack

08+ Infiniti G37 Coupe Parts

Good luck.