If you're manually entering Lat/Lon, make sure you use something like EasyGPS or GPSBabel to export a GPX file from the unit, then load into Google Earth as kind of visual gross error check. The entry interface is not so good and errors are easy to introduce.
The Etrex unit should have a rose indicator showing ground track and a choice of either course deviation indicator or bearing pointer. Remember to use the CDI for navigation from one point to another along a specific track.
Without the database, it may not have magnetic data so will show True courses. Not a big deal as long as you fully understand what information the unit is providing - Read the Manual!
The Etrex is fine for simple track logging, I used one to check the accuracy of my tracks for both DR navigation and IMC NDB tracking/holds. There's a free site called GoFlying that can take the track logs and convert to 3D profiles in Google Earth.
However, I'd echo the comments above - it's a lot of work programming waypoints when other products are available with a built in database for not a lot more money.
-j34-