removing doorlock

[oldscoolcart]

On my 340 1.4 -a streetside parker- some criminal moron from my neighbourhood seems to have put some material in my drivers side door lock.
Nothing visible from the outside, but the key can be hardly turned: movement of it is clearly less than on the other unaffected door.
Spraying some oil into the lock did not help.

Can I remove the lock from the door and open it to see what has been inserted, and remove that and open the lock and reuse the lock? (don't want the struggle to find another lock and having to deal with an extra key).
Where can I find instructions to do this?

Thank you.