I've opened my fujitsu U904, because of display hinge issues and to take a look at the possibility of a harddrive change.
But then i noticed that on the LTE module there are three socket for antennas. One is labeled "main", another "GPS" and the third "aux". Guess what, there is no antenna connected to the GPS port!!! So then I took the "aux" antenna cable and plugged it into the GPS port and now the gps reception is good. I don't use the LTE modem right now, so I didn't test it. But it still has got one of the two antennas so it should be fine.
The display hinges are screwed into some plastic part, which is broken -> seems unrepairable, but it still closes and openes, just has a lot of play.
The harddrive is easy to change, only a piece of foam keeps it in place.
The battery should also be easy to change.