Yes, when it says "Establishing GPS fix" the tablet has started the GPS receiver and is looking for the satellites. Before you run that, make sure that your position in AGPS is set, and the cache data is valid. If that is done, start Maemo Mapper and in the menu (under GPS I think) turn on "Show Information". If AGPS is working correctly, it should say you can see 0 of 12 Satellites. These numbers may differ, but if you have a clear view of the sky, the first number should start going up. You will also see a bar graph with black lines. When these turn to blue, you have a fix.

EDIT
You should only ever have to open AGPS once (unless your default position has really moved) AGPS should automatically update the GPS cache when connected to the internet. As for getting a fix, I can sometimes get a fix in less than a minute with good AGPS data. Make sure that that tablet has a good view of the sky (towards the equator works best). The GPS receiver is in the same corner as the N810 LED I believe, so I always make sure that end is at the open end of the case. (if I have the tablet in the case)