help: trying to center a button in a text widget

What is the best way to center, or otherwise align, pad, marginate (a word?) the contents of a text widget? I've inserted an "<a href=" link ref for the button into the text widget and the button is crammed all the way over against the left side of the widget.

Sort of in conjunction with the above: I am right in assuming that CSS changes done in the "Theme Options" CSS Inserts are stored in the WP database and should therefore survive either a WP or Atahualpa update?

Would setting up a "child theme" CSS file be an option? All my CSS changes/additions could be placed in the "child".css

I hope the above doesn't make it sound too much like I know what I'm doing.

Tnx Jim