Sharla
If the querent is represented by the moon (cancer rising), then as also the moon is a co-significator, do i still and only use the moon for the querent, or do i use another planet instead/too....i.e for a female, would i use venus ?
No you're stuck with the Moon LOL.
If Venus or other planets are in the first, then you can use them, because if the other significator aspects such a planet, it's aspecting the first house and therefore the querent.