The phone should automatically light up when a call comes in. (Or did you mean when you've missed a call?)
As far as having the screen turn on when you recieve a text... I've yet to find anything in the menus of the default Messaging app... But there are alternatives that offer that functionality. (I can attest to the fact the Go SMS has it.)
Is there a way to have the phone light up when I get a call or a text?
Look into Handcent SMS. I installed that on my first Android phone about a week after getting it and have NEVER looked back. It's extremely customizable. Alternatively, you can leave it alone "out of the box" because the default settings are pretty awesome.
Rather that making a completely new post, just edit the first one.
To edit your post just click on the "Options" button in the upper right hand corner of your post, and click edit. You have approximately 1 hour or until someone else posts (whichever comes first) to edit your post.