...assuming that my /programs0 creation script has been used, and that preinit.d works etc. It also assumes that you have a machine capable of running python scripts.

ftp empeg
site rw
put hack_init
site chmod 770 hack_init
cd /programs0
put gpsapp
chmod 770 gpsapp
put incar
chmod 770 incar
mkdir routes
bye

Get a shell prompt (serial or telnet if installed)
rw
./hack_init
rm hack_init
ro
quit

Make sure your config.ini has car_rate=4800 in the appropriate place.

At this point, after a reboot, GPS should be selectable from the hijack menu, and it should start with the satellite strength meter - if you see lots of pretty bars then proceed.
If not, then you need to debug your hardware - ensure that your GPS receiver is in NMEA mode, that the RS232 connections are correct (the sled is wired as DCE with 12V on pin 4, the empeg itself as DTE without the 12V - wire accordingly. Actually this RS232 stuff should have been mentioned at the top...), and that the receiver has a current almanac etc. If your receiver doesn't support NMEA then check the other protocols that gpsapp supports, change the protocol variable as appropiate in M50gpsapp and re-upload. If you use a protocol other than NMEA then the satellite signal strength meter wont work anyway, and you'll just have to see if you can get a fix reported to the empeg. In gpsapp, press down to access the menu, and then press right until you get to toggle co-ordinates. Press down again, and you will hopefully see your current position - Proceed...

At this point go to mapsonus.switchboard.com.
Under general options ensure that "Show long/lat" is enabled.
Get your driving directions to wherever...at the bottom of the page should be "raw route description". Save this as wherever.html
Run parse_mapsonus.py wherever.html > wherever

ftp empeg
site rw
cd /programs0/routes
put wherever
site ro
bye

Now when you start gpsapp you should be able to load 'wherever' as a route. Enjoy.