Sorry to hear about your Arduino. Are you sure it's fried? They are usually pretty tough to break. I would check the Installation and Troubleshooting forum and see if maybe it's just resting... 
Why China? Do you know there are plenty of places in the US to purchase them from?
On your questions, my understanding is that the "P" array contains the data, which includes the temperature reading and the "CRC" is the checksum against the data to ensure it is correct. You don't really need to use either of them, just the results of the calculation on them (the temp). They are in the sample code to show what is being read from the sensors for troubleshooting etc... The "addr[]" array contains the address ("R") and yes it is a global variable that is the same in both startTempConvert and readTemp for any trip through the main loop.
I believe I read somewhere the order the sensors are returned from the search is related to which one answers first, second etc... and I think they will always be returned in the same order, not by the code, but by the nature of the 1-Wire bus. That being said I don't think you really want to count on them being returned in any order since if you add/remove sensors everything will be thrown out of whack. Your 5 "if" statements is heading in the right direction, but I would use an array of the addresses and check them in a FOR Loop.
willnue