Which part should I order?

One day I found our Nintendo Switch on the floor and the left joy-con was in a weird angle -- I think someone stepped or sat on it, so the rail was now slightly pulled out of the joy-con and as hard I as tried, I could not push it back. I could also see a bit of cable stuck between the rail and the case. But everything worked, so my kids continued to play. Some weeks later my kids brought it back to me and now the rail was back in its place, but the Switch no longer reacted to any movement on the left joystick. I bought a new pair of controllers, but I'm itching to take this apart and see if I can fix it.

What repair kit should I buy first? (I would have bought the tools to open the case first, in case some wire is loose, but I didn't see a kit that only had those tools, also, perhaps it makes sense to buy the cable, too, since that could have got damaged.)