First thing, do some tutorials, now...
Layouts can share event sheets, when you create a new layout it will ask you if you want to make a new event sheet, just say no if you don't need one.
Yes you need a layout for each level and the functions to change it is in your events, have a play and you will find it.
An easy way to re-use all your sprites from previous layout is to duplicate the current layout and then modify it as your next level.