Can someone help me who knows about the Nissan Frontier water pump issue?

My brother has a Nissan Frontier which has some serious issues. It's only a few years old, but has mileage beyond the warenty. Anyway, he had an issue where he had an engine problem and a coolant leak. He took it to a shop, and they replaced the water pump. After he got it back, the engine indicator light came, and had the same problem with the water pump, and had a coolant valve replaced or something like that. Anyway, had the water pump go on him yet again, and now we suspect it is something within the engine block. We suspect a cam might be bent, and that is causing the issues with the water pump. So that is the background, here are my questions.

1) Does the Nissan Frontier have a know issue that causes this?

2) If it isn't a known issue, what could it be?

3) How much would it cost to fix something like this?

4) Even if it is fixed, how long with the repair last? Should he just consider trading int instead?