I believe the top part of the case is held in place with 3 or 4 clips on either side. You will need to take both side panels off to access these clips and push them through so the top of your case comes off. Then you can remove and clean your dust filter as needed.
I'd suggest scythe fans if you don't mind the lack of LED's. They're very powerful and very quiet. I have 7 120mm and 2 140mm scythe fans in my case and it's quieter than my mates old Dell with only 2 fans.
If you're certain you want LED fans though, maybe something like this will do?..