Atmega32u2 to USB

I need to wire the Atmega32u2 to usb for my project and the only part thats missing is the part marked with X1 as seen on this diagram:

My guess is that this is a 16mHz crystal but I want to be shure before I do anything.

Scroll down 1/2 way, the Uno uses 32U4 (similar but more memory) and 16 MHz crystal and two 22pF caps are used.
Are you planning on thru hole? SMD?
If SMD, this little guy with 0805 size 22pF caps works great.
Use CTS406 footprint in Eagle.
Here it is on a '2560 board I offer

This one is bigger and also works very good also
Here it is on a '1284P board I offer. The pads were intended for an SMD HC49 size part, but I ordered the smaller one by accident and have been using it or the smaller one above ever since.

I found a little 3.2x2.5 mm 16mHz crystal that I will suit my use. It has four solder pads, two of which are ground. Do I need to solder those two pads to ground or does it not matter?

Part number/Digikey link?
Can't say without seeing the datasheet.
Some ground the cover for more noise immunity.