We did this exact removal in our last house and it wasn't too bad. All the items people are mentioning below are indeed what had to be done but it wasn't a ton of work.

The biggest problem is that the work that is required involves a lot of different skills, most of which i did not have so wound up having someone come in and do 90% of it. tuning up internal drywall and baseboards is pretty easy, but i definitely did not want to screw up my exterior wall.

... and of course you absolutely should not mess around with gas lines on your own.