I have 2 PR640NDRT water heaters. One of them seemed to have stopped working (water was warm yesterday).

1.I changed the setting on other from A -> B. Burner came on and I smelled some gas. Is that normal for that to happen? I called my gas company and they said they are sending someone over. Not sure if this is a free service or they going to charge me

2. How do I check if the Pilot on 2nd is ON. What can be the causes of it suddenly stopping work.

3. How safe is this for a DIY thing?

Thanks.