Coordinates are Cartesian coordinates referenced to the centerpoint of the model. You know, x/y/z. It works the usual way a Cartesian coordinate system works. Type in new numbers to move it around etc etc.
(Or rather, in PCS2 it's -x,y,z wrt. the FSO engine but don't worry about this except for fvec/uvec and if you're trying to use PCS2 to reference nebula trail origins on a non-symmetric model.)
You don't swap textures. You edit the texture, because you don't work with ****ING TILEMAPS
, okay? But to rename textures simply select the texture from the texture list on the left hand side panel, then change the name in the right hand side panel.