I'm sorry, but you have some advice I wouldn't follow from a previous poster. According to my lactation consultant, 4-8 weeks is the best time to introduce a bottle. Breastfeeding is well-established and the baby is more likely to be amenable to breast *and* bottle feeding.
If you pump and then nurse, you're setting the baby and yourself up for foremilk/hindmilk imbalance. It's better to nurse, then pump about half an hour later. I find that pumping in the morning gives me the best yield in one session, but I sometimes end up pumping at night because of convenience.
I also have overactive letdown. My daughter (now five months old) has just adapted to it because it's what she knows. (The advice about expressing some milk into a cloth first is a good one.) When she was first getting bottles, we used the level one nipple. It worked great. Then we stopped giving them by mistake (husband was awfully tired in the evenings and I was a little protective of my "stash" for when I returned to work, so I didn't push him) and started up again around three months. It was a real struggle getting going with a bottle again until I switched to a multi-flow nipple. Since it's early for you, I'd definitely start with the slowest flow nipple to see how it goes. We use Born Free, and feel like the nipple is reasonably similar to a breast compared to some bottle nipples. However, my lactation consultant has become a huge fan of the Breastflow bottles. (We already had Born Free from when our older daughter was born, so we stuck with that.) She said that a baby has to work the mouth in a very similar fashion to actual nursing.
Oh, and no, the slower nipple isn't likely to be preferable to her. In my experience and based on what I've read from others most often, it's when a bottle is faster and less work that a baby is more likely to develop a preference for the bottle instead of the breast. Not that it always happens in those instances either... just that seems to be more common that way than in our situation.
As you can see, you'll get almost as many opinions as you'll get answers. You might check out www.kellymom.com for more breastfeeding advice.
Congratulations on your new baby!