Try this. I didn't finish it but it is essentially the same in reverse once you have fiddled with the handle itself. I recommend protecting the paint because the handle is an awkward fit and it is easy to scratch the door.
1 10mm Socket/Spanner or small adjustable spanner
2 Philips head screwdriver
3 Torx 30 key or driver bit
4 Small/fine bladed screwdriver/knife.
5 Masking or insulation tape
Alfa Romeo Part Numbers:
The part fitted was number 50501304 which is suitable for a 2001/2 model car.
1) Manoeuvring the handle within the external opening to re-attach the wires which open the door and release the lock.
2) Re-fitting the window controls panel so it sits flush.
DOOR PANEL REMOVAL SEQUENCE
1) Remove screws from lower edge of the door panel (1-4 on pic x).
2) Remove thumb pad from internal door handle.
3) Remove electric window control panel
4) Remove the retaining screw from below the armrest pad.
5) Pull Window opening control box out of its slot in the door armrest and disconnect the two electrical block connectors from the underside.
6) Remove both of the fixing bolts which secure the handle to the door panel using the T30 Torx bit.
7) Apply masking or insulation tape to the painted surfaces of the door around the external door handle and around the edge of the internal panel.
8) Working around the edge of the door panel prise the panel away from the door ensuring that you level as close to the retaining clips as possible in order to ensure they do not break. They will pop out cleanly if perpendicular to the hole they are clipped into but have a habit breaking if stressed.
9) When the clips are released (gently pull the panel away from door so that you can check if any clips are still attached) lift the panel upwards to detach the rubber window seal from inside the top edge of the door. Note: at this stage the internal electrical connectors for the speakers and the ‘door puddle’ light will still be attached so it will be necessary to remove these before the door panel can come away completely.
REMOVING THE EXTERNAL HANDLE
10) Pull the weather seal panel gently away from the top right quadrant of the door panel to allow access to the forward retaining bolt of the external door handle. The remainder of the membrane can remain attached. Pull the membrane out of the way and secure loosely using masking tape.
11) Release the handle’s forward retaining bolt with a 10mm socket or spanner by either i) accessing it through hole 'A' shown in (FIG x) or by reaching through the larger hole 'B' to the left. Note: Take care not to drop the nut into the door body.
12) Remove the second bolt on the end of the door using a Philips screwdriver.
The handle is now unsecured but is still attached to the two stays which operate the door opening mechanism and the lock.
When I re-fitted the inner door membrane I used a bit of mastic to ensure a good waterproof seal where the original bead had been broken.
(of course it doesn't help much when I refer to pictures but don't post them, does it!