I am not an expert but have done a lot of reading on the removal of mercury fillings. When they are removed, unless the dentist uses a specific, high-powered suction and keeps the room air filtered, the mercury powder can be a problem. IMHO, it would be more dangerous to get them removed now, just from what I have read.
The x rays, I used to be a dental assistant years ago, I hope they put a shield over you, usually from the neck to about your knees. If it is a newer x ray machine, they have very little radiation but still should be protected when getting an x ray. You are actually exposed to more radiation walking on downtown street where there is a lot of cement than with a dental x ray, I didn't know that until I asked when I was concerned.