Oven takes a long time to preheat

Hi, I am having trouble lately with our gas oven. It takes a long time to preheat and sometimes smell like gas. It does eventually get to temp but about 3 times as long as usuall. I have never worked on an ovenbefore. I am kind of handy so I do not mind getting into it a little if someone can point me in the right direction. Or if is going to be to expensive maybe I will just purchase a new one. It is a Maytag Performa gas.