It is strongly recommended that you keep the Dock showing.
Doing so allows you to see at a glance what apps are running. If you are Close/Quit challenged, it almost certainly more than you think. (Running apps have the little black triangle.) Close applications you are not using, it leaves more memory for other things.
It also becomes easier to drag files to applications to open them. This is critical for people running both Archicad 7 & 8 multiple versions of AC.
If the Dock is too big, click and hold on the 'joint' between the panels to resize it.
In AC7, you may have noticed a problem where Cmd+Opt+D doesn't work for drag a copy, and instead shows and hides the dock. In OS X 10.2, there is unfortunately no solution to this other than to change the keyboard shortcut for drag a copy, or to use the context menu. In 10.3, you can turn off the shortcut in System Preferences | Keyboard. I recommend that you do this anyway, in the spirit of this post. (In AC8, you should break the Cmd+Opt+D habit and use "Cmd+D Cmd" instead.)