It turns out to be much easier the second time. I bought a '16 recently, and of course the new cars don't come with the heated/cooled cup holders. I grew very fond of those, so I picked one up on eBay a couple of days after I got the car.
Actually, the eBay sale was for the entire console, but I convinced the seller to just send me the cup holders for a lower price and avoided shipping a huge box.
The first time I did this, I took the cup holders apart to see how they worked and how to wire them up, then I removed the whole console out of the car, swapped the wiring harness for the console, then soldered a jumper wire. All, as it turns out, unnecessary.
Here's what I did the second time:
1) Scoot the seats back all of the way, then lift up the transmission bezel. I didn't take it all the way off, I just lifted it and rotated it out of the way.
2) Pull the driver and passenger console kick panels away from the cup holder area. They don't need to come all of the way off, just enough for clearance for the next step.
3) Open the center console lid, then use a plastic trim tool to pop up the rear side of the plastic bezel surrounding the cup holders.
4) This is the tricky step. The front of the cup holder plastic bezel isn't held on by the normal metal clips, it uses plastic tabs. There are some openings in the front where you can insert a small tool to push the plastic tabs in on the two plastic pieces. If you just try to yank it up, you'll break the tabs. Once you push the tabs in, the bezel will lift up.
5) After the bezel is removed, take out the screws holding the cup holder and slidy-door thingy in place. After they're out, you can lift the cup holder out.
6) Pop the cup holder connector up from where it is secured to the console, then disconnect it.
7) Here's where it might be different on the older cars. From what I remember, the connector for the new cup holder will plug into the same jack as the old one, but the older cars might not have all four wires going to that connector. Someone will need to verify this. On the '16 car, the connector had all four wires on it, but one of them (the red/blue rings wire) wasn't live.
The four wires in the new cup holder are (my numbering is not related to the actual connector!)
1: Ground
2: ACC (12V when car is on) used for powering the heating/cooling element
3: ACC (12V when car is on) used for powering the red/blue rings when heating or cooling.
4: Dash lamp, so the blue rings light up when the dash lights up.
On the connector, the ground wire is closest to the dash wire. The two ACC wires are next to each other on the other side.
Ground is the black wire with the white stripe.
Dash lamp wire is the orange.
One ACC wire is pink, the other one is white or light grey, can't remember..
When I plugged the new cup holder in the car, the rings lit up with the other dash lights, and the cooling/heating worked fine, along with the tiny LED indicators by the switches, but the red and blue ring lights didn't work. I figured that the current draw from those lights was trivial compared to the heating/cooling element, so I just used one of those hinged plastic wire splicers to connect the pink and white wires together.
The only drawback to this solution is that I'm pretty sure that the voltage at the wire splice is significantly lower than 12V due to the current draw from the heating/cooling elements, so the colored rings may not be as bright as they could be if you wired them to a different 12V source instead. The cup holder is a pretty well-designed piece of hardware, and it has its own switching power supply inside of it to boost the voltage back up regardless of how much is lost in the wires going to it.
After you test everything out to make sure it works, just reverse the steps to put it all back together. All in all, it should be a pretty fast swap.