ML 320 tranny slippage
 

Hey guys, new to the forum. Pretty cool site. I have a 2000 ML 320 with 56,000 miles on it. The tranny started slipping a month ago along with the cel going off. Would get to 3rd gear and hesitate and sometimes stays stuck in 3rd. Also a 4 to 5 second delayed reaction when shifting from drive to reverse and vice versa.
Took it to Autozone and got it tested and the trouble code P0700 came up. The guy said the code meant transmission control system malfunction. Has anyone ever had this problem and if so can you please provide some input? Also never had the tranny fluid replaced. Thanks everyone.