The symptoms you describe do sound very much like those of PMR. Unfortunately it isn't unusual for someone already suffering from one autoimmune illness to contract another. If a diagnosis of PMR is confirmed, then steroids remain the most tried and tested treatment and, rather than feeling wary about taking them, perhaps they may even help to control your Crest Syndrome. I hope you get a definitive diagnosis soon.
As I understand it, the risks of steroids in CREST syndrome are at higher doses and low dose pred is often used to help the stiffness and pain of patients with arthritis. In PMR the pred dose should never be above 15mg which is, relatively speaking a low dose. What treatment are you already on?
As MrsO has said - it isn't unusual for someone with one autoimmune disorder to develop the symptoms of another! This most likely to be because any of these "syndromes" is not the disease itself but the symptoms of an underlying problem with the immune system which makes it not able to recognise your own body as "self". The symptoms vary from person to person and the name of the disorder is based on the records of the first person to observe it and give it a name. So your are "labelled", if you like, on the basis of the pattern of symptoms. Then you later develop some that are not usually associated with the thing you have - so you are said to have "overlap".
Good luck though - hope you have a good specialist. Who are you already under for the CREST?
I live in Christchurch, New Zealand. You may possibly recall that our city has been devestated by earthquakes and one of the upshots of this, is that many people have relocated and we are very short of rheumatologists. Have an appointment in April so shall let you know the results!
Paracetomol with codeine seems to keep me at a "workable" level-I think I have high pain tolerance!
It definatly sounds like pmr my symptoms were similer, but sorry I cant help you will anything else, good look and hope to here from you after you ve see the doctor.