when would my car need a transmission flush or is that even necessary?
on 2009 Mercedes-Benz C300 4MATIC

was told that along with my service A my car needs a transmission flush because one wasn't done at 30,000 miles.

how many miles on car now?
it has 49,290 miles
all data rec every 80k miles but ck with your local dealer
ok should also be in my maintenance booklet manual right?
yes you may want to do it a little early if anything
1 more answer
You should have your transmission fluid changed based on your auto manufacturer's recommendation, it usually every 60,000 miles.