Sat Nav Retro Fit for 2009 Impreza WRX 2.5

Hello,

I have a Subaru Impreza 2009 WRX 2.5 hatch, it has the CD player head unit, I am considering installing a Sat Nav depending on how much is involved. My preference would be to fit the OEM one as the car is totally standard and unmolested. There seems to be OEM Sat Nav units available for about £250. Can anyone tell me what is involved in getting this to function once installed? Are there any codes needed before it will work with my car / ECU? What about updates etc? Can it be used as a navigation unit free without a subscription (Starlink)?

As you can tell i don't know a lot about Sat Nav units but I have been working on cars a long time so installing it is no issue.

Thanks for your help,

Dave