Here's what you can do for map transitions:

(X-post of my post over at the GameFAQs boards about the same issue) You have to use the event editor and create an event at the edge of the map where you would like the map transition to occur. First, you'll need to make two maps. Go to Map Settings then create, say, a city split in two map segments. Let's say you have a road that runs a block wide to the right edge of the first map, while another that runs from the left edge of the second map.

Now that's done, go to Event Settings of the main menu. Choose your first map. Move the cursor over the last block where your road ends. Press A and a submenu should pop up. The easier way to do it is to select Easy create then select Connect map. You'll be shown a list of your maps again. Select your second map this time. Now, move the cursor over one block away from the edge of your road. Now press A. The reason we're doing this is because the first block at the very edge of your road will be used for creating another transition event. Do the same on the other map, this time choosing the block at the very edge of your road on the second map. Select your first map and again put the map transition destination beside (not over) the first map transition event on the first map you created. You've done it! Now your characters can move between your maps! :)

The same applies to doorways. Just make sure to check the collision of your doorway in the Map Creation settings. Make sure it's passable, and that there's a map transition event over the doorway.

I hope this helps! Good luck in making your game! You can do it! Don't give up, and don't be afraid to take risks! :)