Install the BGW320 gateway

We have U-verse over fiber network. Recently had an issue with one of the TVs giving 'no signal' error.

After chatting with customer service, I received the new BGW320 gateway to replace the current one. 

I do not have the technical knowledge to do it myself.

How do I get a technician to come and install/replace the current setting? 

How much do the technician cost?