2002 TDI transmission problems

[coilman2645]

I have a TDI JETTA, purchased the car new car runs perfect until yesturday. the transmission is starting to slip on the highway. The car has 219,000 kms. and it spent most of its time on the highway. The car shifts ok in every gear in town but on the highway when it goes into overdrive it is'nt always a clean shift. On the highway the car wants to down shift if you push the peddle to much and there seems the be some slipping in over drive.
Do you think the oil should be changed, if so what type and brand do you recommend.
Doug