kop9000 you can just put it in a function...
I added a function you can call whenever you need to show dialogue. In this case I'm positioning the dialogue box in relation to the player, but you can pass X and Y in the function if you prefer or have a fixed dialogue position.
Also, I added an array with all dialogues and use the array X as a dialogue id for the elements that call dialogues.
Just try the example and check the code. Use space to start dialogue or advance it.
EDIT: I just read the bit about changing speed. You can do that passing the speed on the function if you want...