Macbook Pro top case not functioning

It may be something as simple as the ribbon cable to the top case (which runs the keyboard, backlight, and trackpad) has become disconnected.

If you "google" up "replacing macbook pro hard drive" it will lead to to several tutorials on how to properly disassemble the top case.

The connector for my MacBook Pro 3.1 is a very shallow socket on the cable that mates to a raised square on the system board. There should be a small strip of Kapton tape to help hold it in place. Kapton tape is an "anti-statc" tape used in the assembly of computers.

If that checks out, you could be looking at a defective ribbon cable or a defective mate surface on the system board.

But always check the obvious. "Is it plugged in?"

I have yet to see a "defective" hard drive cause the keyboard and trackpad to stop functioning but still permit the unit to boot up and be used.

However I have seen a defective keyboard / trackpad that would prevent the unit from booting.

Do the lights on the keys still function?

My first inclination would be that the ribbon cable is not seated fully or properly to the system board. On mine it is very difficult to ascertain that it is mated fully and the least bit of disturbance will pop it right off. That is why the tape is so important.

If you have verified that and still want a replacement you would need to look around online auction sites etc. I would also see if your local Apple repair station will sell you one.

You may also find a dead unit you could scavenge parts from.