Volvo c30 T5 bj 06 Automatic transmission rinsing

Good day together Would you like to have a few experiences about automatic transmission oil flushing at the Volvo C30. First of all to the story: Ride a C30 T5 automatic bj. 06 186400 km. I’ve been thinking for a long time about a flushing of the transmission but nothing was acute so far. Was however a few days ago with the car on the Nordschleife and after a few kilometers came the display in the Tacho “Griebeöl temp. zu hoch”. That made me already a bit stutzig then… anyway then first A few days later I noticed, however, that the gearbox is in a position when switching from R to D a slight cracking noise makes that definitely not there before. Today I was in the workshop then… The gearbox is in order, but there is a little bit of oil in it. I was advised to have a flushing done. Cost point 850€. Supposedly, the oil filter alone would cost 250€. Find that quite he I found an oil filter at sxandix for just under half of the time.. but would also have to know the exact name of the transmission… Maybe someone can help me further. mfg Marco