I think the best way to import Google earth data is to use bob's track builder. http://www.bobstrackbuilder.net/
I think it's best to get the pro version so you can export to rFactor, because there are tools to deal with rFactor to 3ds max etc.
There is an article here on how to import google earth data in .KML format to bobs track builder.http://www.nogripracing.com/forum/showthread.php?p=694036
Basically you map out your path on Google earth. Don't put points too close together as you will get spikes in height. Also don't complete the loop, leave a small gap between the last point and the first point.
Then save place as .KML file to desktop or wherever. Then use http://www.gpsvisualizer.com/elevation
and load the .KML you have created into that and add height and save as .GPX.
You can then use 3d.route builder, http://hybridgeotools.com/html/downloads.html
(demo is free) to import the .GPX file.
Note you can only export upto 500 points with free version.
You then press ctrl+A to select all and go to route-altitude-update from geotool.
This will open it up in Google earth and check heights. When you have done that you have the option to smooth if you would like. to take out any dips or spikes.Then export as .KML again.
Import into Bobs track builder. Select all samples and closed circuit. and there you go
From BTB you can output it to rFactor, then using isi tools max plugin or 3dsim ed you can import to 3ds max or just convert to .3ds format.
Hope this helps