There is also an air pump that holds vacuum while the car warms up which is located in the fender. My 1999 1.8t Passat had fuel line issues when the temp got that cold...it would actually leak until warmed up, I guess the crimp was bad or something.
It could be a clog in your drain. In my case, if I do not run the garbage disposal before the dishwasher, it will not drain properly (our dishwasher drain pipe connects to the drain at the garbage disposal). There are lots of possible causes though—check the Dishwasher Not Draining wiki for more detailed help.
Typically, not always, the center pin is the positive. You can test this with a voltmeter. As long as the voltage is the same on the adapter and on the device (also, I have 9V DC and 9V AC adapters, do not mix these up) and be sure the current required is less than the amount that the adapter can source otherwise you risk overloading the power supply. I go to thrift stores and pick up spare adapters all the time, if you know what you are doing you can cut off the plugs and match up the voltages. Saves a bit of money but if you do not have the experience it might be better to just buy a universal adapter.
You need a VAG-COM cable to reset most codes on these cars as well as to do many other procedures including resetting certain convenience items such as chimes, window and lock behavior. Ross Tech sells them as well as the software. I purchased one of the ebay knock off cables and I am using the free software from the ross tech site. This cable is good to have if you do any of your own work. Great for checking codes and in many cases you have to have it to complete procedures (throttle body adaptation, transmission fluid checking).
Reflowing the mobo in the oven would not be advised in my opinion due to the fact that the parts on the bottom can drop of since it is a double sided board. I would use the heat gun reflow method. There are many videos on Youtube. Much easier, be sure not to overheat or bump the board while it is hot. Otherwise, you are pretty much doing the same thing that is done during manufacturing. From what I have researched it seems to be issues with the BGA (Ball Grid Array) under some of the chips as well as poor heatsink compound. Some people have had good luck with the reflow and new heatsink compound (artic silver is best).
Sounds like you might have blown the amplifier in the deck. Hook the RCA outputs into an external amplifier of some sort and see if there is sound there. Also, I second markus on check all the wires. Plus this time before you put it back in be sure to cover all non used wires with tape or something to prevent shorting. The amplifier turn on wire shorting for example has been the cause of many blown decks.