United have more problems than just LVG. I don't know the club well enough to understand what these problems are, but every time I watch them it is the most boring football I can tune into throughout all of Spain and England. I'm not sure if this is entirely LVG's fault, but United should definitely be doing better with the set of players that they have.
LvG's Overall Record
Louis Van Gaal has already lost more games with United than he did with less than 2 seasons at Bayern. He has the worst overall winning record of his career with United. He is certainly not living up to his potential, especially since he has been afforded arguably more transfer funds to get the players he wants than he did anywhere else.
1) Should he be sacked?
2) If so, who should his replacement be?
IMO, I think we should stick with him for the remainder of his contract and give him that one more season. Let him bring a couple of more quality signings this January or Summer and we'll see what happens next. We are good enough to get top 4. But the title seems to be going City's or Arsenal's anyways and those teams haven't even clicked yet.