@JohnFromGWN Thank you so much for the quick reply! You're correct, I don't have a lot of mods (mostly clothing, cars, and couple trainers).
And sorry if I was unclear... the sirens I'm referring to are the ones that play on the intro startup screen (after the broken window sound, gunshots and stuff). I wanted to share that to say it doesn't get very far before it crashes (it doesn't even get to the part with the character illustrations!)
I'll try the steps in the article you sent and post here if it worked. I did place the files from my backup folder into the game files folder and I feel I might've messed things up more since now it crashes even sooner than before (before I did that it at least got to the character illustrations before crashing).
I also tried uninstalling and reinstalling so I'm not sure what's going on and afraid I really messed up... But fingers crossed, I'll try the tips from your link, keep troubleshooting, and post if I have any luck! And if you think of anything else your expertise would be greatly appreciated! Thanks again!