I used a Medela Pump in Style, i got it used from my co-worker for $75. I think it's important to get a good strong one like this one. Only the motor part is used, everything else you can get new. I'd go to a place like Day One or Natural Resources and have them help explain the pumps and things you need. All those parts can be intimidating until you figure it out! They also have free magnets to put on your fridge with guidelines about how long to store milk, and I bet you can download the simple chart with the guidelines too. But generally I think they say 3-5 days in the fridge, and up to 3 months in the freezer. That might be conservative.
I pumped 2x a day at work, but when I first went back I did it 3X just to be sure we'd have enough and to maintain my supply. But 3x didn't last long and I went to 2X on a regular basis. And if for some reason I didn't nurse him at home before bed, I'd pump then (or any other time I didn't nurse when I would typically nurse). I kept the Pump in Style at work and had a small hand pump (Medela brand) for times at home, which were rare.
Have fun, and congrats on the new little one!