All Things Event Hacking

Zeemis' great tutorial will explain how to do the custom title screen. Thanks to everything he provides, it's really easy. http://www.youtube.com/watch?v=29q6SY9XAyU

As for question # 2, you would want to open the event dump and find the event in question. Then look for the 6B, or (load map) command. This is what it looks like.

CC/985F: 6B Load map $0017 (Narshe, mountaintop (WoB / "Long ago, the War of the Magi...")) instantly, (upper bits $2000), place party at (18, 25), facing down

The first part of this string of commands, "the 6B, XX" is the first map that is loaded in that prologue. So you would want to get the correct address from "C/985F" which is:
"C9A5F" and go to it. You will see "6B,17" Which is "Load map, Narsh Cliffs"
Changing the 17 value to something else will generate you a new map. To know what map you are changing it to, open up the Level Editor, "FF3LE" and it will tell you what map is what, or rather what byte to enter, on the left side once you click the arrow.
You'll notice that 017, or "$17" is "Narshe, Outside, Northern Cliff."
Just know that to load the maps over 100, you will need to look at this excerpt, taken from this very thread.

"How to use the maps over #99 (maps that are more than 2 bytes) -
The third byte after the 6B, xx, is the second byte of the map to load (the high byte) but it also has various flags it can use to determine other things. The highest two bits are used to determine the direction you face when the map loads, there's another to indicate the location name, and I'm not sure what the others do. Basically, if you want to use maps 100-19F, set the lowest bit of the third byte. 20->21, A0->A1"

I hope that makes since.