Faulty auto gearbox ???

I took my 2015 Vauxhall Insignia to main dealership for annual service . The garage told me fault codes showed that my gearbox was showing numerous deficiencies and suggested it was not repairable and quoted approximately £6000. to replace. Having used Wim/auto many years ago decided to pay them a visit complete with diagnostic report. Ken read the report and suggested there were too many faults for the gearbox to be working at all. As the car had only done 51000 miles with no record of any oil change it was decided to flush and change the oil, to which I agreed,this was done immediately and I was shown the works done by video. These works were done 3 weeks ago and since then the cars transmission has never been smoother. Please use Ken and his team whenever you have a problem and beware of main dealers. The Tops.