Hacking Nintendo DS Lite Shoulder Buttons problem

[ZereoX]

Since I have my DS, the shoulder buttons have been less and less responsive (30% of the time) but now they simply don't work (2%). I saw at Dealextreme, Replacement switches but I'm wondering if the problem is my DS's motherboard or the actual switches. Is there a way to figure it out?

P.S: Don't post about the method of sealing your lips around and blowing, it helps momentarily but will eventually erode the inside.

Thanks, ZereoX