Baking problem with my gas range

Sometimes when I set the bake cycle, the oven will take a long time to heat up, sometimes up to an hour. Sometimes we smell gas, and sometimes there is a small explosion (pop) sound when it finally lights.
The broiler cycle is fine, and so are the top burners, just the bake cycle.
I set the temp, then push start. There is a click and I can see the glowing element come on under the pan down below that stays on the whole time.
Last night I listened real close and it sounded like the gas was sputtering.
I think the gas reguator valve (if thats what its called) must be faulty.
I would like to save some money and replace this myself, so I am wondering if I am correct, what is the part called that I need, and is it difficult to replace?
Any help is appreciated…