Is this car safe to drive?

I own a 2007 nissan altima and the oil was not changed properly several months ago. . ALL the lights came on for awhile, then the car died on me in the middle of the road. . There was a lot of crazy noises in the engine. I took it in and they "cleaned it out" said a bunch of gunk and stuff was in the engine. . like oil and sludge. . so now my car runs diff. . I always am in panic when i drive it. . occasionally when I start it a bunch of white smoke comes out of the tailpipe. I had the oil changed again somewhere else and they said not to worry. The brake light came on for just a split second while I was driving today. I have smelled something burning one day. Another day I smelled rotten eggs. The car just does not drive the same. I feel in panic like I can go anywhere. . but no one will tell me whats wrong and all the dealwer said after they cleaned it out was we cant see if anything is wrong or what is wrong. . but wouldnt the lights all come on again if the car was going to die again or short out or something??