I have had problems with the trunk lid - my wife never seems to be able to close it tight and it leaves the light on - I usually find out when I go to lower the top and it doesnt open until I close the trunk properly. The struts on mine are getting harder to open and close and the wife never gives it a tug to make sure it locked.

As far as 1 tail light goes - this has a Euro? park light system and you can leave either side on - there is a P with an arrow for left or right - check your headlight switch and make sure it isn't in the wrong position. (should leave a front light on too but worth a try)