The G820 works great for what you are describing. I have been using these units for several years now with great success.
To make life easier for you change the G820 static IP from 192.168.0.35 (default) to match your AP address, i.e. 192.168.1.35. This way you can access and check signal strengths etc. without setting a static IP.
You can plug the G820 directly into a computer or use another router if you need more than one computer or wifi at the remote location. Supports VOIP quite nicely.
With the standard antenna RP-SMA you can add directional and/or higher gain antennas.
If you haven't bought the unit yet I would suggest looking at the Meraki Minis
Meraki.
These units are inexpensive and work exceptionally well. Being true MESH units they can solve a lot of problems regarding interference, just dog leg from another building using 3 boxex, i.e. AP ==> repeater ==> repeater.