I've only just returned on-line from a 30 hour re-install and I don't have FS2002 setup again yet.
However from memory, the ETE entry is either the time you can expect to arrive at your destination, or the length of time it will take to to get there, both assuming that you maintian your current airspeed.
The FS2002 GPS reports both, I just can't remember off the top of my head which entry does which.
Yep! ETA is estimated time of arrival and will vary as you encounter weather and adjust speeds. Have some sympathy for real time pilots who get ATC on their case because they are 10secs late on a checkpoint