I'm sorry you are having additional complications. If I were you, I'd get a second opinion before jumping straight to steroids for muscle and joint pain, especially when it is of such recent onset. First, look at all your medications to see if that is a potential side effect. A common culprit for that is statins (cholesterol medications) or many other medications with muscle and joint pain as a side effect.
It might also be the onset of fibromyalgia, which is very common with scleroderma. Or it could be that you are going through a stressful time, and not sleeping very well, and the fallout from that is aching from head to toe. In any event, since this is new, first look to medication side effects or any recent changes in your lifestyle (such as stress, or perhaps even stopping a regular exercise.)
As Jo pointed out, its not the best idea to rush to steroids, especially with scleroderma. See Warnings for Steroids and Scleroderma, because steroids strongly increase the short term risk of developing scleroderma renal crisis (sudden kidney failure).
So many other things could be tried first, such as improving sleep, stretching or exercising or warm pool classes, pain medications, massages, antidepressants, muscle relaxers, relaxation or meditation programs....why, the list goes on and on, and most of us use a combination of several if not many things to address muscle and joint pain.
You've just had the whole stress of possible lung infection and difficult questions regarding possible treatments added to your plate. That's quite a stressor, too, and probably won't do anything to improve your relaxation and sleep (and thus, it may increase your joint and muscle discomfort.)
I'm unable to take any steroids, even apart from scleroderma issues, and have managed widespread and chronic joint and muscle pain for decades without steroids. So, I know it's possible, even though steroids are certainly a very fast shortcut, in the long run, they can be quite troublesome, especially with scleroderma. Such as Jo, who has had to have two hips replaced just in the last year.
I also count myself lucky to be unable to take steroids. I'm positive a single dose would have me hooked forever, as it would be a single source for relief (rather than the more complicated steps of sleep evaluations, plus other medications and many lifestyle changes) and I imagine it would be instant, as well. So then I'd spend my remaining days incurring kidney failure and joint replacements....of that, I have little doubt.
Pay very close attention when you are being counseled regarding treatment, and take the time you need to make a proper decision. Some things truly are better off not treated, because sometimes the risks of treatment really are worse than the risks of the disease. Especially as we age, we are more likely to encounter ailments that we are better off trying to just live with, as long as possible, rather than tackle them head-on. But, you don't hear people talk of these issues much, for as a society we tend to go all-in for any treatment that exists.
I myself have chosen to not have some things treated, yet have gone all-in for treatment of other things. It's helped me to ask my doctor, if it was them, or their loved one, would they attempt this treatment, under these same circumstances? A surprising number of doctors would personally forego treatments that they are still obliged to offer to their patients.
I'm sorry, I don't know why I'm going on and on about this. Except to say, I appreciate that you will be faced with many decisions. Some may have easy answers, some not. Who knows, maybe you could even try the steroids at low dose for a few weeks, just to get the worst of the fires put out, while you work on getting other approaches ready, such as perhaps some good sleeping and pain meds, or enrolling in a warm pool class. Just be aware to do your best, working with your doctors, to try to avoid relying on high dose or long term steroids for your condition -- if it's reasonable and possible, under the circumstances.
And please bear in mind, none of us, particularly me, are doctors, and we should not be guiding your medical decisions; rather, hopefully just giving some food for thought or to discuss with your experts.