You're giving us no information whatsoever to help you. The 325i spans across 4 generations of the BMW 3 series; we don't even know what year yours is. Are you stuck on figuring out one part of the job, or are you asking about the whole process? Take a look at this, see if it gives you an idea . . it's about replacing struts, but there's a brief section in it about springs:
What is your mechanical ability? Overall this is an easy job on any 3 series. Yes the front is a little more time consuming then the rear, which is a breeze, but still nothing that his hard. You might want to swing by an autozone and rent some spring compressors but other then that, simple job when it comes to a DIY.