Photography help? (extra characters)?

Okay, so basically, I'm going to be taking pictures of this fashion show that's going on at my church, and I wanted some suggestions about a few things.

Is it "bad" if I were to leave my camera (which is a Nikon D3100) on auto the whole time and never doing anything manual, even though it's a fashion show?

The lighting in the church is kinda dim. If I were to use my manual settings on my camera, what would you suggest I use?

Try using some manual control. This is because auto will not let you control any of the picture that you will produce, meaning that it will probably produce a long shutter speed in dim conditions. This will be problematic for fashion photography because you want to freeze the models in action.

So, if you're not greatly confident with using full manual, try using shutter priority mode and dialing in at around 1/160 of a second, if not higher. Set the ISO to about 800, yet you may want to lower this if you plan on using a soft flash.

For shots when you don't have much time to prepare, you can use full auto but you'll have to use the flash to maintain a high shutter speed. Hoped this helped and good luck!

The only time I use Manual Mode is when I'm using studio (manual) flash or blending flash into the ambient, for everything else I use Aperture Priority.

There's only one level of light on the sensor that will give you a correct exposure, aperture, shutter speed and ISO all have to balance, if you increase one you have to reduce one of the other two by the same amount. It makes not one jot of difference how you achieve a good exposure, whether you let the camera work it out (recommended) or whether you use manual mode and guess (or meter).

In Aperture priority you set the aperture f5.6 or so whatever depth of field you want. Half press the shutter and the camera will tell you what shutter speed it's having to select for the light level you have available at the time. If it's too slow, up the ISO, it will make images more noisy but you get the shot. You can try a wider aperture (lower f number) but that might make focusing more difficult as DOF will be narrower.

Pentax has Tav Mode which is ideal for this kind of shot, you set the shutter speed and aperture and the camera alters ISO to get a correct exposure.