In the various civil war drill manuals, what we would generally refer to as a regiment were called battalions for drill and command purposes. Technically, a battalion was two or more companies. Actual prepatory commands and commands of execution would have used the term batallion instead of regiment i.e. "Attention - Battalion" or "Battalion -Forward - MARCH."

As to your particular question, a change of front means that Lane was changing the direction of his line. Wheeling the entire line at once was too cumbersome, so it would have been done simultaneously by the various regiments. Here is how it would have worked.

Let us assume that Lane wanted the line at a 45 degree angle to its present position. The first battalion [regiment] presumably on the right of the line, would have re-alligned itself on the new line, with the right most man being in the same position, only facing 45 degrees to his right. The succeeding regiments would advance forward ande then conform themselves on the new line. There would have been a variety of ways the individual regiments would have accomplished this.

There is a great collection of on line CW drill manuals at http://www.zipcon.net/~silas/links.htm#N_7_ if you want to get to the real nitty gritty.