Finished and things are running smoothly after Titanic proportion disaster. 3 Things:
1. Nearly ruined the whole job on the last step putting it back together. I used the OWC dual SSD install kit and tools and the OWC digital thermal sensor for the replacement HDD. I combined the two OWC videos and also used iFix-it's instructions. I installed the WD 2TB Caviar Black in the first bay (replaced the original Seagate 1TB) and installed the Samsung Pro 850 SSD where OWC said. iFix-it has you remove the optical disk drive and put it behind that, but some posters said they thought that would block air flow. I used OWC's location which doesn't require removing the optical drive. However, I removed the optical drive just to have better access to install the 2nd data cable on the back of the logic board (hardest part of the install...well, maybe not...). Once I had the data cable plugged in, the rest went back into place without much difficulty. The very last cable you plug in at the top left (first unplug in the break down) was my pitfall. I left the iMac 27" on its stand. Without the glass and the LCD, the iMac leans all the way back; I couldn't figure out how to lock the stand in one place. Not to worry, I'll just hold the LCD in place like in the video while I connect the cables. On the very last cable to connect, you guessed it, the LCD flips out of the case and onto the table! All the previously connected cables came undone. Luckily, there was no apparent damage to the LCD (fingers crossed). Two of the cable connectors were damaged by being yanked out. The LCD thermal sensor was the worst. I spent quite a while carefully bending the two copper prongs back to their original position. I didn't think of it until afterward, but the thermal sensor on the hard drive I removed had the same connector type. Regardless, I spent several hours and multiple attempts to connect the LCD thermal sensor before I had success. Once I got the machine back together, I powered it up....it worked. I loaded the Snow Leopard install disk and formatted the drives separately...that worked. The OS install worked...Whew! Do I tell my wife? I don't think so. Regardless, I can boot the OS from either drive, and I'm using the 2TB drive until I figure my next step. Lesson to those attempting: figure out how you will secure the iMac in the stand while reinstalling the LCD (and also while removing it).
2. I restored the latest Time Machine backup, which unfortunately was 3 months old. The only thing important missing is all the pictures of our kids' Cross Country season. I put the pictures from my wife's camera SD card which has many of those pictures, but not all. The TM backup also is missing some pictures from before the last backup. You can see blank pictures in iPhoto with a thumbnail, but no actual picture. Not sure how that happened or how to fix it. I have several TM backups in a sparsebundle file that goes up to Sep 30, 2014. At one point I found another sparsebundle that had a Dec 29, 2014 date, but I can't find that now. I have 2 3TB Seagate external drives that I've used for TM backups. I think the problem is from switching backup disks using Snow Leopard. Any advice on how to use TM to find that missing backup or how to find the missing photos in the backup I have would be very appreciated.
3. How should I run these drives? Right now I'm not using the SSD because my intent was to set up fusion. However, the SSD is only 128GB and I needed to use the 2TB WD to restore the TM backup. Do I need to upgrade from Snow Leopard to make fusion work? If so, which OS should I use? Mavericks and Yosemite are both free, but I've heard many awful things about them. I'm happy with Mt Lion on my MBP, and I think it's only a $20 upgrade for a new disk. Or, I could manage things manually and run the OS and apps on the SSD and use the WD as storage. If I do that, can TM backup both drives in the same backup, or do I need to run separate backups?
Thanks for reading. Hope your install goes better than mine.