I recently sent off my d-300 unit to Nikon for a cleaning and general repair. The focus had gone soft. I got the camera and lens back but it will not focus under my normal shooting conditions. I shoot wildlife so I usually shoot in C, burst mode with spot metering and focus. I have tried EVERYTHING and every setting. My subjects are often moving so I typically use a shutter priority mode. I have an important trip coming up and need answers.