Hi Guys

I was wandering if anyone could help me with a few questions...

1) I have a flight booked going to Vancouver from Dublin via Amsterdam (Economy). I was wandering what way it works fees ways. I would like to change my flight coming home to a couple of weeks earlier. I saw it said there is a changing fee of 100EUR...do you have to pay the different between flights or just the 100EUR or wot?

2) Is there a limit to how close the flight you can change it?