1. (walkinintheseshoes) you would connect the blu/white wire from your aftermarket deck to the blue wire of the wiring (antenna up). I would also connect the amplifier remote turn on lead to this wire.
2. (muzza69) you havent got the yellow (constant power) wire connected to constant 12v+. Im not sure whether the VL had this wire in the stock radio loom so you may have to run a wire straight from the positive terminal of your battery (fused within 30cm).
3.(allanssv6) You cant connect RCA cables straight to the stock headunit, it dosent have the outputs, you'll need whats known as a line out converter (LOC). This has to be connected to your standard speaker wires and converts these into RCA outputs. Its ok just to "tap" into the wires so the speakers are still connected. If you wanna runa subwoofer, i would tap into the rear speaker wires where they run into the doors just behind where the seatbelt is in the b pillar. Be sure to solder and tap each connection.
The LOCs are offered by a number of companies, but i havent had much trouble with these.....
Jaycar Electronics
4. (Insanity) Did the power antenna work before you rewired the plug so the constant power was connected properly? If so then i would check that the blue wire in your stock plug (power antenna) is getting power when you turn the stereo (and the tuner/radio) on. If not then connect the blue wire on your stock plug to the antenna output wire on your aftermarket wiring harness.
As always, any questions...just pm me