A normal filling doesn't go that deep and doesn't interfere with the nerve of the tooth.
A root canal involves drilling deeper and removing all of the nerve of the tooth. The tooth will die and you will feel no more pain from it again. This will enable you to keep your crown - assuming the procedure is successful, as there is a very small percentage that fail.
There is quite a bit of drilling involved, but it's painless as the area will be numbed .... it's just a bit uncomfortable with all the drilling - but if you want to keep the tooth/crown, it's worth it in my opinion.