Problems with DSLR - help fast?

When I put my 18-70 mm lens on my Nikon D70, the top right corner of the screen flashes F- - and will not take pictures. The only way it will take pictures is if I put it on M, and when that happens the picture is dark and nothing shows up. Adjusting the ISO does not help. I have tried taking the lens off and on again, many times. This has never happened before. When I put my other lens on, it's fine. Any tips, I have my first big photo shoot tomorrow! Thank you! I will be happy to add add'l info if you need it.

With the lens attached but without pressing the lens release button, turn it gently (don't use force!) as if you were attaching and disattaching it, i.e. Wiggle it a bit in the lens mount. It may be that the contacts didn't attach properly. You may hear a "snap" when they do.

If that doesn't work, then check if the contacts are dirty.

If there's an aperture ring on the lens make sure it's on the biggest number. Also sometimes f means format your memory card (a problem with the d70). Try reinserting your memory card or formatting it. Hope thi helps