Suggest replacing your balljoints at the same time. Once you have gone through all the trouble of removing the control arms, this is cheap insurance against having to do much of the work again any time soon.
Consider the condition of your struts as well, since you will be doing most of the labor towards their replacement.
If you replace the struts and balljoints at the same time, you should be able to forget about the front suspension for 100k+ miles, which is comforting.
You certainly would need an alignment when the control arms are removed, though you may try to mark the current position so that they will be close enough to get to the alignment shop safely. I just used a burst of spray-paint, since my MB is far from being a showcar.
I also had to cut one of the control arm bolts on each side to get them off. They were corroded in place for good. Like you, I live in a 'roadsalt' zone. A Sawsall worked well for this.