If the battery hasn't been replaced before, which is probably the case, you will need to remove the existing battery, install a battery socket (which will need to be soldered onto the board) and obviously a replacement battery.  Not overly difficult but not as straight forward as replacing batteries on say a DE or WMS/Bally machine.

If you aren't comfortable with doing the work yourself, I am sure there will be plenty of guys on here that might be able to do it for you or get in touch with Ken Shipley - you will have your board back within a few days and his work is always top notch.