Folks, I don't think he's after a world map at all. I think what he wants is a PICTURE of the world map that the player can call up from items or something, to get a quick overview, and then put it away again and be right back where he was. Like a map that you can carry around with you to get an idea of where things are in relation to your current position. Hence the need to make the player sprite transparent. I don't think he wants something that you can walk to different locations on the world map and be transported to one of them (that'd be a bit hard if the player's invisible - you wouldn't see where you ARE, so would only guess as to where you need to go).
If you don't want to go down the route of creating a picture and using Show Image, here are a couple of other options:
In the item's common event, before sending the player to the "world map", record the current map number, player's x and y in variables (and to make it look more realistic, player's direction as well). Then send them to the middle of your "world map".
If the world map only takes up a single screen, make every tile impassable. Put an event right next to the player's position in all 4 directions, triggered by Action Button, and all 4 will transport the player back to the saved map, x and y position (if you recorded direction, you'll either need to reset the player's direction via script, or use conditional branches in the event to send them back - one for each direction, since you can't specify direction using a variable).
If the world map is larger than a single screen, make every tile passable so the player can freely move using the arrow keys to make the map scroll. Add a single event set to Parallel Process. In this event, have a loop that waits 4 frames then does a conditional branch: If Input Button C is pressed (I can't remember what the option is called exactly, but if you can't find it, shout, and I'll go look it up for you), then move them back to the original map, original coordinates, original direction and fix their opacity.
Actually, that second option would work even if the map IS the size of the screen, so I'd probably go with that one regardless.