I will tell you how I added building. I am no expert btw.

1) You need to add it to the MX_Building.xml (just copy and paste dwarven settlement).

2) Change this line
<Description type="Unit" subType="Building" ID="ABb1" Name="Dwarven_Settlement" Description="Dwarven Settlement">
to
<Description type="Unit" subType="Building" ID="ABb2" Name="Dwarven_Settlement2" Description="Dwarven Headquarters">
- You need to give it and ID (i don't think it matters what as long as the ID isn't already in the game (and maybe only 4 digits), I just made it ABb2 for ease)
- The Name="Dwarven_Settlement2" is what links it to the mx_Building_Data.dat
- Description="Dwarven Headquarters" Is the name it will have in the game.


3) Now you need to add it to the mx_Building_Data.dat (again just copy pasting the dwarven settlement entry there)

4) Change the very top bit:
[Dwarven_Settlement]
to
[Dwarven_Settlement2]

5) Now you make your scripts and add them, can't help you there I'm afraid. You would change these entries though:
(Lived_In_Script Lived_In)
(ActiveScript Tower_scan)
(BasicScript Tower_scan)
(BackScript Tower_scan)
(birthscript basic_birth)
(birthScript2 Guild_Birth)
(IGdeathscript Guild_destroyed_a)

Check the file:
ms_prototype.gpl
It has some useful details in it.

Good luck!