Amanda, for now just keep topping off the PS reservoir with ATF (yup, automatic trans fluid -- DONT use regular PS fluid from the store).
I have had mixed opinions about the replacement. Some people say it is just a matter of being able to get underneath the car -- others say that it is a royal pain on the behind. either way, yes -- you need to drain the fluid. I have all the parts to do it in my apartment, including all the clamps, nuts, bolts, and even a new reservoir -- I should be able to report back in the next few weeks.