There is quite a bit to getting the LS programmed. Things to consider is where to ring if called externally(I would setup a ring group with as many of the remote phones as possible), this is done in trunk attribute it also should have a specific class of service and perhaps class of restriction. You will need a circuit descriptor, likely the default value will work, maybe a couple of setting changes. The harder part is setting up the dial out restriction or what I would do, some type of zones and location based number setup. You might also need to create a tone file to add a delay to the system dial out. If you are uncomfortable with all these forms, you might want to get your vendor involved and let them know your plan regarding 911. You could point them to this discussion and I'm sure they would follow the reasoning here.