I have recently upgraded my sound system and deck in the car. I drive a 2012 Jetta trendline+ (I guess S?) 2.0l gas 5 speed. Taking the front bezzle off surrounding the deck is not too hard, you can pop it off by sliding in a credit card and using it as leverage (just don't unplug the air-bag plug at the bottom). Then you need 4 torx screws to take out the stock deck. I replaced mine with a Kenwood DDX371 (approx. 300 bucks, has BT, DVD, Aux, USB but not at the front). To install the deck, get a Metra wiring harness, Metra front plate, and a Metra antenna cable (unless you do not want AM/FM radio) off ebay. Ebay is cheapest and should run you around 60 bucks (depending where you live). In my area (Toronto, Canada) many shops and stores overpriced these parts like crazy, so my suggestion would be to get online. The wiring harness plugs into the existing plug that you removed from the stock deck. Then enjoy wrapping the wires from the new aftermarket deck to the loose wires on the metra harness. For your power cable... you can either get an expensive adapter (I didn't do this), or run an accessory cable to your fuse box and connect it to a remote fuse (one which powers on with ignition). Alternatively, and what I did, is splice into one of the red cables that is present from the original radio plug. Just make sure it receives a constant 12 v with a multimeter. By doing it this way, you have to manually power your radio on and off everytime. However, the advantage is you do not need a key in the ignition to turn it on. To add, if you want to bypass the DVD safety thing (it won't let you watch movies unless your "parking break is on"), just connect the blue parking cable from the deck to ground. Easier than actually finding the real parking wire god knows where in the car.
For the USB and Aux cables, I removed that center storage tray thingy that sits just below the temp controls (where your cig holder and aux port is). To remove it, pop up your shifter panel (again I used a card) and then that will reveal the center tray being held by 2 torx screws. Remove those and you can remove the tray after unplugging the 12v outlet cable and AUX cable connector. I decided to get creative and made custom ports for the USB and Aux connectors. You can buy USB and AUX extension cables (male to female cables) for pretty cheap. I measured then drilled holes in those little square pieces (which are removable) to fit USB and Aux female headers. The male ends were then connected to the back of the deck (there is a hole there at the back which goes from the top of the deck to the bottom of the tray). Now put the tray back in same way you got it out. You can now tuck the mess of cables in behind the deck, screw the faceplate onto the deck, and re-insert it in the hole (and line-up the faceplate to the torx screw holes). Re-screw the deck in and snap the bezzle back on. You should be now all done.
As a side note, the old AUX connector is useless now. I personally took it out of the tray and replaced it with a switch that controls the parking cable to ground connection. It is kinda useless, but effective if for whatever reason you want to disable DVD. You could alternatively just leave the old aux socket, and know that it is not connected to anything.
Let me know if you have any questions or if I made no sense or if you have suggestions to my method. I could post pics for you guys if you would want. Let me know if you want pics and what you want to see. I also did install a sub and amp so let me know if you want info about that as well.
-p