How hard is it?
Texture modification - very easy. Just open the textures and edit them, or make your own and name them the same as the one you want to replace!
Hardpoint editing - allso easy. You can download the Model Property Editor from BCfiles. There are TONS of setting, and alltough it is easy to change some settings, there are many, so it takes time.
For instance - a single phaser has about 60 settings:
colour(inner, outer,...), damage, recharge rate, discharge rate, max damage distance, max charge, 3D coordinates, fire angle, 2D icon position, repair complexitiy, hitpoints, is it targetable, critical, phaser inner radius, outer radius, cone radius, etc.......