i have a 97 lumina with the 4t60e, and a month or so ago the "service engine soon" light came on, i took it to advance auto and they put their computer on it and said it was a transmission code, but couldn't tell me what it meant. i have changed the fluid, filter and had the code reset, but it came back up in no time. the symptoms are, hard shift into 2nd gear, and higher than normal RPM at interstate speeds (70mph = 2700-2900) any advice would be great.

For 70 MPH those are not unusual R's for that engine & trans. However if the r's are varying that much on a level road, for gosh sakes take it into a trans shop!!

Based on the limited info you have lost overdrive in the trans.