as for importing it to the garmin, plug garmin and go to my computer. open up either the garmin folder or the memory card folder and then open up the folder called new files, it should be empty. put the .GPX file in the file called 'new files' close down the folders on the pc and unplug garmin. start the garmin up and under where to from the home screen click on saved items or what ever it is, under there should be your route
if some of the folder names are wrong you'll have to excuse me as i don't have the garmin to hand ATM
do that tonight as it can take a bit of playing about to get it right the first few times so import the route and check it's on the garmin properly tonight.
as for recording whilst navigating, yes. simply set the navigation as above and then simply start riding and press the physical play/pause button as normal to start and stop recording, simples