You can tell if the disk is spinning by noting the orientation of the disk when you insert into the PlayStation. Then, on the XMB, check to see if the little loading wheel is in the upper right hand corner of the screen. If it is, press the eject button. If the disk came out in the same orientation that it went in, then you should first try cleaning the lens. If it still does not read any media, then you likely have a faulty lens.
If there is the loading wheel in the top of the screen, and the disk comes out at some different orientation, then you likely have a disk issue. Try a different disk. If that doesn't change anything, then try the method previously described for a faulty lense.
If there is no loading wheel in the upper right hand corner of the XMB, then you likely have a faulty daughterboard. If that is the case, you are in a tough spot, as like Chris said, the two boards are "married" together.
Good luck, and let us know how it works out.