Does the engine have to come out replace timing gear or chain on a 1994 cavalier?

No, the engine does *not* have to come out to replace the timing chain (or belt, depending on the specific 1994 Cavalier engine) on a 1994 Chevrolet Cavalier. Access is possible from the top and/or front of the engine. However, it's still a relatively involved job requiring specialized tools and a good understanding of engine mechanics.