Ronny,
da ich diese Fragen schon im PMDG-Forum des öfteren beantwortet habe und ich zu faul bin, das Ganze nochmals auf Deutsch zu schreiben, hier meine Anleitung auf Englisch

:
Paint the full_left and the full_right (don't forget to mirror any writings on the right side). Then save these, merge all the layers in the full_left and copy it into the clipboard. I would recommend to close the full_left.psd WITHOUT saving it. Now open the pmdg_700_fuse_t.tga (I never use the pmdg_700_fuse_t..psd) and paste the full_left from the clipboard into the two upper quarters of the pmdg_700_fuse_t.tga. The second quarter should start at an offset of -911. Repeat this with the full_right pasting it into the lower two quarters of the pmdg_700_fuse_t.tga. Save the TGA and convert it with DXTBMP (saving it without mips!).
Grüße
Thomas