Replacing OEM radio/dvd with OEM radio/dvd with navigation

I am replacing a oem radio/dvd in my 2013 Cruze with a oem radio/dvd with navigation out of another 2013 Cruze. both cars are LT1. i know i have to have the replacement radio/dvd with navigation flashed with my cars vin number. i have the following questions

1) There is an extra antenna port on the back of the replacement radio/dvd. Is this for an GPS antenna?
2) What other cables/harness will i need to purchase to get the GPS to work?
3) Is there any other modifications i will need to make to have the GPS work on this oem radio/dvd with navigation?

thank you for your help!
Sterling
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