Running lights replacement issue?

Hello, so are only the rear tail marker lamps working? Looking at the wiring diagrams, there are two rear marker lamps per side, and the License plate lamps are on the same circuit. Are those working? And with this change over, did you purchase a kit that came with resistors for the replacement LEDs? And do the front marker (Parking) lamps work okay? I see an option for your vehicle where it can come with front led parking and turn bulbs. Or just regular bulbs which are all on the same circuit.
As for the fuse change over, I assume they told you to change the Tail Fuse 7.5amp? And my last question, do you have voltage at the rear marker bulb socket?
Some of these changeovers can be tricky when going to LEDs, since they need a current limiting resistor in most cases, or the 12-volts on that circuit will burn out the led the first second you turn them on.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

It depends on if they have the resistors possibly built into the unit. So, what happened with the first two sets, did they work then stop working, or have you had no lights working back there since the crash? Because the front Marker lights are on the same fuse and circuit as the rear taillights, so if the fronts are working, then there has to be a wiring issue. This is the problem with crashes, it's hard to tell exactly what may have gotten damaged. I will look through the OEM diagrams and see if there are any connectors you can check in between the front and rear. But a little more detail about what happened with the 1st and 2nd attempt to get the rear taillights going will help.

And the Reverse lights are functioning, okay?

Okay, I'm not worried about the accident part, we're here to get it fixed, that's all. When you say he changed the polarity, did he do this with the LED lights? Possibly switch power to the ground side of the LEDs? Because LEDs are diodes, (light emitting diodes), and a diode will only allow current to flow in one direction. So, reversing the polarity would do nothing, especially since your taillights were working before the changeover. I was reading through the info from the link you posted, I would go through and recheck all the fuses. There was a warning about disconnecting the battery before trying to install this set for whatever reason.
Below I'm posting the OEM diagrams and I only see one connector between the front marker lights and the rear taillights, and I think they even may have it labelled wrong. In the 1st diagram, the connector labelled EB1, there's no eb1 connector, so it has to be BE1 which is in the second diagram, pin 10 of that connector (third diagram, green wire) is the feed to diagrams 4 and 5 (green wire) which is your tail and license plate lamps.
Since the power for everything, front markers, parking lights and all the rear marker lights goes through the Tail Relay to that 7.5amp Tail fuse and then branches off and the only connector is that Eb (Be1), I would go to that connector and see if there is power there on pin 10. If not, you'll have to start going through all your fuses thoroughly.
I can't see how the fronts are working unless that connector got messed with or is not making a good pin contact inside. It can't be a bad ground since your Brake lights are working.
I'm also posting the aftermarket diagrams so you can see the entire circuit. But let us know what you find.
I added the warning I found