Is this command necessary to actually "enable" the internal GPS receiver? "

Specifying a "File Path" causes Maemo Mapper to use libgpsmgr to try and start and GPSD server using the given path. If GPSD is already running, then libgpsmgr may return a failure (but I thought it was supposed to do nothing - maybe that's libgpsbt I'm thinking of, though). In any case, you already have a GPSD server running, so you shouldn't use "File Path", you should use "GPSD Host", as you did in your second try....

Hm. If it doesn't produce an error, then it sounds like you've connected to the GPS receiver, but have not yet received an NMEA sentence. Usually, GPS receivers will send NMEA sentences even when they don't have a fix (i.e. with satellite info). If you're not getting any NMEA sentences at all, it sounds like the connection isn't really working that well. In fact, you really should be getting an error after about 10-15 seconds.