First time installing a mod and I broke everything - help

Used a YouTube tutorial to install a vehicle add-on. Now when I try to play, the game gets stuck on a black screen on startup, then crashes.

What I did: put the .rpf file in the dlcpacks folder, edited dlclist.xml, launched the game.

What I should have done: installed a memory extender? Also backed up first?

How do I roll back? Verify game files through Steam? Or do I need to delete something else?