the speaker grill is connected to the door trim. the trim is easy as to take off. i have a vx sII. and i kno wthat the vt is the same so yeh. unless u can pop it out from behind the door trim. i dunno. door trim is simple to take off. there are more screws on front doors to the back doors. they wil have some screws in side of door that swings open, some on botton of door when open, one on the side that the hinge is on, one in the door handle, pop the plastic cover out with a sharp stanley knife and there is one inside there, handle just pops out. pop the red insert out of the door lock, and one inside there, take them all out and there will be one more inside the space where the door handle sits, (need to remove handle to see the one behind one for handle). it is easy as. it should just slide up and pull away simple.
hope it helps, i have had my old vt and mums old vx ss and my vx exec all off. as i am a stereo gook and yeh. have changed many stock holden speakers