D60 Shutter Error And dark photos

I have been receiving the press shutter release error and have tried about every little fix I can find. When in Manual it will give me an error every time. When in auto the camera will work but gives me dark, underexposed photos. I have tried cleaning the red wheel, done the reset, tested different settings with the lens on and off and I’ve checked the lens (ok there). I’m beginning to think it’s probably a bad sensor or something? Nikon actually suggested to just buy a new camera because it $250 just to ship and look at it. Then plus repairs it could go up to more than half of what my camera cost. I cannot do that and think it’s ridiculous to do so unless I know for sure it’s something major (which I don’t think it is because everything else works fine. ) I am tech savvy and can work in most things but I don’t want to mess this up and take it apart again unnecessarily unless I have a pretty good idea what may be the problem. Any suggestions? I have no camera stores anywhere near me so that’s not an option unless I ship two states away. Thanks for advice!