Big Al,
In general, it isn't a good idea to overwrite any files associated with a default aircraft. Doing this can effect how fs2002 loads each time you open it. If you want to add a texture to the default 734, then add the folder and edit the Aircraft.cfg file accordingly. To remove one of the default textures, edit the .cfg file but do not remove or overwrite the texture folder.
Also, make sure the texture you are adding is designed for use with the default aircraft rather than a different model!
Good luck!
Erik
