1. You can use teleporters to link from a dungeon entrance to the dungeon. Placing the teleporters is emu-dependent, but if you tell us which emu you're using, someone will probably be able to help with the commands.
2. To make a map2.mul, you have several options. You can create a map0.mul using your favorite map maker, filling in extra space with water, mountain, or whatever, then use a program like UOCopy to copy it into the correct size map. Or you can use the Map Generator software at
http://worldmaker.ryandor.com/, which can make maps of any size. Then you just use teleporters to get from map to map (or write spells, or provide items, etc.) Again, how you move players from map to the other is both emu and situation dependent. If you describe how you want players to be able to shift between maps (moongates? spells? teleporters?), someone may be able to provide more details.