ECM Replacement - '06 ION 2 2.2
 

Hi Folks!
My girlfriend's Saturn 2006 ION 2 needs to have the ECM replaced. I plan on buying a used or remanufactured ECM and doing it myself. I've been unable to find much information on the details for how this is done.
1) Flashing or programming the ECM. Does this have to be done by the dealer? If I buy a second hand unit, does it need to be done at all?
2) The numbers on the ECM...Not sure what they mean.
a) There is an unlabeled 8 digit number at the top: 12604805
b) 8 digit "Service Number": 12599726
c) 4 letter code of some kind: YMUK
d) This: gm06e04h01
And a long 16 digit alpha-numeric number below a barcode.
I found what I believe to be the correct ECM online, but I am not clear on what these numbers mean as they do not match 100%.
Does anyone know of a resource that could guide someone like me in the ins-and-outs of the Saturn ION ECM replacement? I searched the forums here, but my search for ECM pulls 0 results.
Thanks in advance!
-Aaron