If you're the original owner you're covered. You should have all the info you need in the warranty booklet in your glove box with your owners manual. If you're not the original owner, the warranty has expired.
Yes, the water pump is covered.
Call Isuzu and ask them where they want you to take it.
Isuzu Support- 888-464-7808
Isuzu Warranty- 800-235-2464
Isuzu Owner Relations- 800-255-6727
I hope those phone numbers still work.
Mark