Don't worry about trying to see the laser... i've taken my psp apart numerous times and know the parts inside out and can verify that i still can't see a laser on both of my working psp's...
My first question... Have you made any mods to your psp casing?
cause i know when i swapped my casing i had to fidget around with the umd door a bit before it read properly (it was also making the same noise your describing)
My second question... The little nub that you press in to make the drive start up, does it make any noise while your pressing it or does it only make the noise when a umd is inserted?
If it makes noise when your pressing it, check to make sure theres nothing gunked up in the gears. If it only does it when there is a umd inserted make sure the umd your using isnt cracked itself and double check to make sure it catches the circular slot that sits inside the middle of the umd when you close the door.
If you need a troubleshooting guide you can check this one out...
http://www.llamma.com/PSP/repair/PSP_UM ... _Discs.htm
Report back with your findings so that i can assist you further.