There's no question in my mind that if easier is the main priority, buying a new NVR is the answer. Even if the parts were easily available, which I think is not the case, you don't know at this point if you need to replace the power supply and/or main board, and/or disk. It could be as simple as replacing a blown fuse, or everything in the case could be fried. If it were me I'd spend a lot of time troubleshooting hoping to save the NVR, likely an unwise choice. I did that a few years ago with some A/V equipment fried by a nearby lightning strike. Spent a lot of time identifying what had failed, only to determine that salvaging any of it was infeasible.