Driver side door lock actuator issue, 2008 C4GP 2.0HDI

[ixus400]

My car's driver side door could not be locked/unlocked by the fob, but ok using key. Other doors are ok. So I think it would be the lock actuator problem, the motor maybe dead (i've seen several videos from youtube on this kind issues already).

So I decided to try to open it, but after I dismounted it, I found it's really difficult to open the box, seems two metal rivets firmly connect the metal plate and the plastic box.

Does anyone has ever tried and successfully opened it with no damage?

And it seems difficult to find this part from the autodoc website, does anyone knows from where can we buy it?

Thanks in advance and expect some helpful replies.