Bill,
Unfortunately it doesn't look super easy, I found a video showing disassembly on a similar S55 model on YouTube here: [https://www.youtube.com/watch?v=JfV1_1cGS7k]
But I can't say if yours would be the exact same or not. I have also heard of Toshiba soldering on the RTC aka CMOS batteries on certain models. On the S55 in the video, it looks "normal" meaning you can just pop it out and put in another "CR2032" watch battery. It looks very doable if your body of the laptop is the same as this one.