You would have to extract the file with Pack3D version 2 from the dat file found in the submarine Interior folder, eg for type VIIC:
Extract
druck_radio_7.tga from
SilentHunterIII\data\Interior\NSS_Uboat7\
NSS_Uboat7_CR.dat
Don't quote me
I think it's the
_CR.dat file, once extracted you can use a paint program to edit then just place the file in the
SilentHunterIII\data\Textures\TNormal\tex folder, and SHIII will use this over the default, if you need Pack3D or the individual files for each of the 4 types just let us know, and I will upload them, hope this helps.

Cheers.