Hi
I fitted a central locking kit to my 2001 Ducato,it was quite easy really.I bought one of those universal kits from Ebay. It never let me down !
After that i had an alarm fitted to it and then the central locking became remote control.The only problem i had fitting the central locking was doing the side loading door.I used the plunger switches from an old Fiat Punto's rear tailgate.They connect when the bootlid is closed ,so i fabricated it to fit the side loading door to then work the central locking .Now the door slides shut and connects.Its a similar principal to what is fitted to Transit side loading doors. As for electric windows ,i never bothered with that.I wasn't sure what kit to go for.
Hope this helps.
Alex