Some of the circuits are shared so if you have removed the fuse that may be why central locking has gone , I am not an auto elec but have had many years in the car industry . I would suggest that if you have a test meter you can set it to continuity and start checking the light fittings themselves the meter will indicate a short to earth so it may take a while to find out what is causing the short also check the manual to see ift tells you what may be sharing he circuit and then you may have to check those as well . If your current radio unit is asingle din you will need to find some release arms these are small flat bits of metal with a 90 degree corner on one end you may find that the bezel around the outer part of the radio unclips you can then insert the release arms and remove the unit . The radio could also be part of your problem .