Extend WiFi range for NVG589 ?

Residential Gateway (RG) is model NVG589, and is located in corner of basement of 2-story home. 

WiFi strength is weak at opposite end of house, and on 2nd floor.

We have Ethernet wires available on 2nd floor. 

1. Can anyone recommend a simple and reliable WiFi extender or access point that can also provide a few wired ports?

2. Are there any configuration changes I should make on the RG so everything works in harmony?