The answer is yes and no. Yes in that it can be upgraded to 16GB and the link was posted by another helpful responder:
You would need to take out the 4GB and 2GB modules and replace them with 2 8GB modules.
If you know what you are doing and can pop of the bottom cover, then the hard drive and memory can be replaced. For that matter the battery as well.
Check Google as there are some YouTube and other posts showing how to pop off the bottom cover (you start by the hinges). If you are not mechanically inclined or nervous then take it to Geek Squad or some other reliable Toshiba service entity.
I upgraded mine to 16GB RAM and a 250GB SSD. The unit boots up in less than 10 seconds and is extreme;y fact at everything I ask it to do.