If you mean whilst studying as a cadet, they get paid somewhere around 1200-1500 euros per month I think. I am sure an ex-student from Luxembourg could confirm or deny this.
As for being a valid controller, the chances of getting into Maastricht are slim to nil, they have only taken experienced ATCOs from other units a couple of times in the last 10 years, salary is good though. I have not worked there but believe it is around 7-8K per month, it will depend on experience etc but again, perhaps a Maastricht Controller could clarify this.
Cheers