Hey S.,
I'm so glad the breastfeeding is going well for you; it's the first wonderful thing you are doing for your baby! As for pumping, easy peasy, get a Medela (it's expensive, but trust me just spring for it and you will never regret it - if you're not going to pump that much, you can even get their single pump). As for bottles, I used Dr. Brown's with my first girl, but am using "Born Free" with my second - they are BPA free and have a very similar design to the Dr. Brown's. Again, more expensive, but having a child who isn't ingesting dangerous chemicals and who isn't getting a lot of gas during feeding is worth it. (Dr. Brown's also makes a BPA free bottle but they have a chemically odor from what I hear). You can definitely do this! I pump every day at work and my daughter takes a bottle no problem... and, no there is no window after which your baby will not take a bottle; it will be new to her, but I'm sure she will surprise you. (I started my first daughter on a bottle at 7 mos! Before that, it was exclusively from the breast.)
As for the actual pumping of milk, pumping does not decrease your supply of milk (Stacy mentioned it might, but that is not the case). When your breast releases milk on a consistent schedule, whether from a pump or from nursing, your body maintains that general level of milk. The more you pump or nurse, the more milk you will produce. The less you pump or nurse, the less it will produce - it might take a couple of days to adjust, but it always does. You need to make sure you are eating well and drinking plenty of water. Personally, the only time I have ever noticed a slow-down in production of milk is when I had not been drinking enough water.
Again, congrats! And just enjoy her!