Plus, remember you have to have special tools around like spring compressor, a press, etc. and you have to get an alingment afterwards.
I also suggest taking a serious look at replacing your struts and idle arm bushing and, at a minimun, changing the sway bar bushings, strut top mount and the drag link (if they are original) while you are there. The latter are relatively cheap!
As far as doing it separate, it depends on time frame in between and the amount of usage of the car. Days? Weeks? Months? Years?