Do like the Ghost said. Read a bit, before you jump.
If you are properly prepared, and you downloaded the drivers you might need, and saved them on a flash drive or something (drivers are in the second link he gave you) everything should go smooth.
It is good to have a USB mouse on hand, in case your touchpad does not immediately work, and also be prepared for the chance that your wifi will not work until you install the proper drivers. But a wired connection should always work.
Hopefully, everything will go so smooth that you will be complaining about all the time you wasted preparing...
I have a C655 with a Pentium chip and 3GB RAM and wouldn't risk putting Windows 10 on it. The system is already slow with Windows 7 and only a few programs on it. With Windows 10 it will be much, much more slow.