Looks like a standard 2.5" form factor.
https
/www.youtube.com/watch?v=qqZT70Ig8ZI
I usually recommend 250GB for a SSD. For optimum performance, you need to keep about 15% of the SSD empty. With a 120 GB SSD, figure 20 GB for Windows, 8 GB for a recovery partition, 20 GB for programs, 8 GB swap, 8 GB hibernate, and you're left with just 38 GB for data. Unless you know you're not going to be putting much data on the laptop, a 250GB SSD gives you a lot more breathing room.