1996 Nissan Sentra Driver side window

The power window on the driver side of my car is not working. It started as just a problem rolling the window up. I would have to "help" the window go up by pulling it up. It goes down just fine but not it won't go up at all. And once it is all the way up is shifts down about an 1/4 of an inch away from the seal. Is this a motor issue or do I need to replace the whole window regulator. And is it something that I can do myself?