Bob

SSD's don't get hot (they barely get warm), so you can stick the temp sensor anywhere on the SSD.

You'll need a mounting tray to mount a 2.5" SSD in a 3.5" space, but these often come with the SSD.

No need to stay with the same manufacturer, I've had a lot of success with various HDD's and SSD's, particularly Samsung. The only manufacturer I've had problems with is OCZ (I had two 500GB Vertex drives fail).

No reason why you can't put an SSD in the iMac. It'll speed it up no end!

A 3.5" SSD would also fit (you'll need an adaptor to fit the 2.5" version).

I've fitted a SSD to my MacPro, and it runs at just above room temperature, so overheating is not an issue. It doesn't get warmer in any specific area, so I'd just stick the sensor where it looks best, and doesn't stress or interfere with any of the cables.

This would be a really good time to change the PRAM battery. They only last 4-5 years, and cost very little. It'll save another teardown in the near future. (3v CR2032)

I didn't see the need to tape the foil to the display (and I didn't want to get any sticky residue on the screen), so I skipped this bit with no problems.

Citation de sebalancea :

there's no need to disconnect the microphone and camera cable. you can work against a wall and carefully rest the frame and the display on the wall.

I didn't even use the wall, I just carefully pivoted the frame backwards and laid it on the table without disconnecting the wires

Citation de mindzeebeez :

These four screws are tricky to deal with. They are well recessed and hard to spot at first. A magnetised screwdriver is a prerequisite. Another way is to glue the screw heads to the screwdriver with some very weak glue, and let it almost set before trying to locate the screws back into their holes whilst re-assembling. I lost one screw somewhere inside the computer! It is alright with 3 but I hope it doesn't touch something vulnerable on the circuit board.

Try sticking the screw onto the driver with a tiny piece of blu-tac. Worked for me.

Citation de mtense :

I found elsewhere that the thermal sensor should be reattached with rubber cement. That's what I used, and it seems to be working fine.

I used double sided thermal tape (available from electrical component stores). It's usually used for heatsinks etc. so it will stick well on a hot surface.