Gateway question

I have 2 houses. One house had a NVG589 in it. I got U-verse hooked up at my second house after putting my internet service on vacation at the first house. I tried to take the NVG589 down to my second house so I am not stuck paying 2 modem fees.
When the tech came to setup service, he could not get the NVG589 to work. Now in the second house I have a Pace Gateway that looks to be quite an older model than the NVG589.
Here are my questions.
1. Can I call customer service and get the NVG589 connected? I am thinking that the address needs to be changed for it to work.
2. Does the Pace or the NVG589 have better signal? I do not have the model number of the Pace Gateway, but it seems as so that the NVG589 is newer and has better signal than the Pace.

Thanks for your help.