doubletree - you can also change the layout on the Maintenance Page
You find it under Design > Layouts on the left column select Maintanance page (yes I know it's misspelled but you'll get use to that on the cart
)
That will allow you to add blocks, enable your contact info if you wish - etc.
A fast way to get to the xml blocks is to go to System > Localization > Language Definitions
if you know partially what you're looking for as in this case maintenance , just type it in one of the fields at the top - like the translation and enter - it will bring up all the xml files that use that term.
In this case it is the index_maintenance Text Message click on the edit icon on the right and you will be where you can easily edit.
This is a preferred method rather than working in the code files - this way it stays in place thru version updates.
Lee
Just another happy Abantecart user!