I just wanted to add that I used to get that "The sims 3 has stopped working" a lot, too, and it has stopped completely since I got Overwatch from Nraas. I do not have ErrorTrap. But, if you decide to get another mod, I can recommend Overwatch. It automatically clears stuck sims in the neighborhood and also deletes the cars from public lots etc. For some reason it ended my crashing, and I'm more than happy.
For instructions I'd say to just read carefully what is posted at Nraas' installation intructions
here. If you ever had any CC, you shouldn't have any difficulty.