Applecare Repair Turnaround Time?

Usually less than a week, and a good part of that is shipping time. But it can be longer, depending on availability of parts and on how many machines are ahead of yours in the queue.

Once you have your case ID, you can track the status on this linked page (definitions of status messages are here).

Hope this helps...

I would also make sure your genius bar agrees to terms such as if it isn't available in three weeks that a replacement computer be offered, and have them put it in writing. There have been a few cases here where it has been reported to be longer, but when I call them, they tell that normally they can offer a replacement when the wait time excedes that length. So just make sure their replacement offer is one that you are comfortable with. If not, ask around at various authorized service centers:

http://www.apple.com/buy/

Often, after 3 or more such "serious repairs". Even then, you would probably need to request a replacement (and should do so, if you get to that point). Having said that, a logic board is just a circuit board (albeit a relatively big one, with other chips soldered to it). It can fail like any other piece of solid state electronics.

That really depends on what the status of your backup is, whether you can agree with them not to erase and information, or to try to recover information first, whether or not you are concerned that a replacement computer may come out and only be able to load a newer operating system, and how much faith you have in their refurbished parts that may be put in its place. Usually it is pretty good either way. Don't forget many logicboard repairs are due to people not knowing how to handle the ports and cableson their computer*:

http://www.macmaps.com/frayguide.html

Not that you are one, but it is something to be aware of.

- * Links to my pages may give me compensation.

As I say, that conventional handling of cables needs to be more careful in the future. The audio being crackly usually indicates oxidation, or scratching from the cable. Only insert straight in, or pull straight out and don't jostle in the port.

Nobody here can say with any certainty, as it all depends on availability of parts and how busy the repair depots are.

Ask Apple and/or the Apple Store. Each case is different.