Replacement Transmission VW Bora

Hi everyone, MIG has suggested posting this on the Mk4 Forum to see if somebody can help, so thank you for any help.

I am new to the Forum, just joined so pretty excited to be part of the group. This is my first car group forum so forgive my lack of knowledge. I have a 2003 VW Bora v5 2.3L , which i have owned for 15 years, it has served me pretty well, bar a few cheeky problems and electrical gremlins along the way and still really enjoy driving it. Recently though the Auto gearbox has given me much trouble, it started with intermittent loss of reverse gear, which then developed into permanent loss of reverse gear, and now it is slipping in forward gear. I wanted to keep the car so i hunted around for a used transmission and have finally managed to find a compatible unit from a wrecking yard. I have called around a few auto trans mechanics about remove and replace costs and am getting varied costs and varied answers regarding the need for re-calibration. Quotes have ranged from $1100 - $3000 and some mechanics have said it should be a straight changeover ( plug and play ) where others have said it will need a new module and re-calibrating ( re-programming )...forgive my lack of tech knowledge here can anybody shine some light on this subject for me please, before i proceed? Thank you very much everyone