In the Owner's Manual for my Rendezvous, I find that at 50,000 miles I should have the automatic transmission/transaxel serviced. On all reports from oil changes and the like, I have never had any mention of any problem with the transmission and we are not experiencing any. I now see that I can get an transmission "flush" or a transmission "service". I do not know the difference except that, I think, the service includes the replacement of the filter. Which is the better choice in this situation? Is it necessary to have the filter replaced at this point?