I would talk to a couple really close friends or family members and write down the names of dentists that they use, especially if they have been going to the same one for a few years and are really happy with the work. Then call the offices of these couple of dentists and talk with the staff about what's been going on to get a feel for the practice itself. You can also look at the dentist recommendation area of this forum to see if there are any near you that other's on this board have found helpful and compassionate.
While sometimes finding a good dentist can be a crap shoot at times, it sounds like you definitely need a different dentist and now. You can always schedule the first appointment as an evaluation of the situation. That way no work is done and you can have a good idea of how the office works and if the dentist is competent, compassionate and caring. This also saves you from getting work done right away in an office that you may not be comfortable with, or flat out dislike, and keeps you in control.
You may luck out and only need to have the filling redone but as Brit said, RC's do not need to be an ordeal. They should not be painful or traumatizing. We even have a couple of stories from members on here that found themselves falling asleep during their's! In experienced hands a lot of people find them easier to deal with then some other kinds of dental work, including fillings. While they sounds a bit scary (the whole dental damn thing and drilling the nerve out of a tooth) they shouldn't be and are a a vital way to save the tooth.
As long as you get this attended to soon, you probably don't have a high chance of losing the tooth. Hopefully there wasn't any further complications of decay under the filling (which can cause them to fail) but even if there was, the tooth can often be saved with an RC.
