I also wan't to be able to remove the 'Comments are closed' text that now exists below all of my posts.

To remove the "Comments are closed." text, add this to your Appearance → Custom Design → CSS editor:

#comments .note {
	display: none;
}

I want the tabs to be evenly spaced out in centre format across the menu bar.

There is probably more than one way to do this. Here's one way:

.nav li {
	padding-left: 67px;
}

Note that if you change the number of menu items or labels for them, you will also need to adjust the padding-left value.

I'm using the Linen theme and currently the main menu bar appears to be left justified. I want the tabs to be evenly spaced out in centre format across the menu bar.

I also wan't to be able to remove the 'Comments are closed' text that now exists below all of my posts.