Volvo Repair: Volvo V79 2001 2.4L transmission, transmission control unit, volvo dealer

Question
hi. I'm confused about what to do re: my transmission. Getting lots of differing advise... I was stopped and car was in Drive.  when I pressed on the gas to go, nothing happend, as if in neutral. then the digital gear flashed D then R then N, and I immediately got a e-message "transmission needs service". I turned off the car and restarted and its been fine for 3 wks. My software is up to date. Volvo dealer says transmission fluid looks too "pink" considering it hasn't been changed in 78k, and does not smells like VOLVO fluid. This car was last serviced by former owner at another Volvo dealer at 52k and receipt says "synthetic". Should I have it serviced? and if so, must I take it to Volvo and pay $400?! Volvo told me the fluid part no. is 1161640, but on another blog I saw 1161540 and that Mobil 3309 is identical. If so, can I have my own mechanic do it? thank you!

Answer
Arelene, That fluid is ridiculously priced.  Yes the Mobil stuff is the same as well as amalie synthetic fluid.  The smell exactly the same.  There may be a relay issue for the transmission control unit giving you an intermittent flash.  Servicing may help but be prepared for the worse if it doesnt work.  These transmissions do fail frequently.  Roger