Phantom II
I'm not an expert and maybe a professional modder here can enlighten you better than I.
They are in dat files that can be opened with skwasjer's
S3D - Silent 3ditor program. I've used it to change onboard photographs mainly.
Give it a try. It's very simple to use.
http://www.subsim.com/radioroom/showthread.php?t=119571
Download at ...
http://sh4.skwas.net/