The sensors aren't difficult to remove from the bike, but I wasn't sure how to open them up to install new batteries. In addition to that, the heart rate sensor has a screw-on cover, and I don't have the right size screwdriver to deal with it.
So, to the bike shop again. I had to go after work, and it was nearly dark by the time I got home. I saw a beautiful sunset, though.
At the shop, I mentioned to the man who was helping me that things were going to get really busy soon. The holiday season is about to begin! He replied that it had been crazy all day. It makes me glad that I don't work in any kind of sales job. I'd lose my mind in no time!