I would say you definitely have a switchpack problem if the rear/left isn't working from it at all. Front/Left... erm, could be switch pack related, but could also be the outstation in the door where the relay is. It's a double coil/contact relay, so by default the output pins to the motor are both grounded - then when you go 'Up' or 'Down' it energises one of the coils to put 12V on one of the wires to make the motor move in each direction.
One thing you could try... pop the door cards off the front doors (you'll need to take the drivers one off to check the latch microswitches anyway). If you swap the door outstations between the doors, does the passenger window then go up? If so, then the relay in the outstation or the driver circuit for the 'up' portion has failed. If it still doesn't go up, and the drivers window still works as normal, then it's the switchpack aswell.
I have a refurbished switchpack without sunroof available on exchange on my website if you do need one.
Tailgate - it does lock/unlock through the drivers door latch, but if that tests OK, then the actual switch in the tailgate is known for corroding aswell.
Hope this helps,
Marty