Can I bring a dslr camera to a baseball game?

Hi, I'm going to a mets game tonight. Not sure if I could bring my camera, I have a Nikon d3100 dslr camera. I also have a big zoom lense.

Read more: Can I bring a dslr camera to a baseball game?

How will I know which aperture value to choose?

I am using a Nikon FM10 and a Lumix DMC-GF2, and for both, while changing the aperture values, I don't see a change in the DoF when looking through the viewfinder.

Is the only to get the right shot is too try out different values and look at the developed pictures?

Read more: How will I know which aperture value to choose?

Where can I rent a high quality camera?

I just want a camera to take some pictures for a few hours so I would need it for less than a day. I want to use one of those like $600 cannon or nikons. Any idea where I could rent one or something?

Read more: Where can I rent a high quality camera?