Coffee50 --
Candlelight will have 2 performances on Sunday -- one at 5:30 p.m. and one at 8 p.m. (I suppose it is possible that it could run a bit late as well).
I would say that the whole Ceremony lasts anywhere from 45 minutes to one hour. Disney will say that it is 45 minutes, but last year the Ceremony was still taking place at 6:30 p.m. on Sunday night, even though it was supposed to have begun at 5:30.
The seats (usually white fold-up chairs) in front of the stage are for invited guests, such as VIPs, invited guests, Club 33 members, media, etc.
There are a few benches (a very, very limited number) set up sort of on the side of Town Square (it would be the right hand side when facing the stage), or around the perimeter. There may be a few benches on the left-hand side as well, but I'm not sure of that. Those benches are for the general public/non-invited guests, and if you want to snag one you have to get there early! People will literally claim those benches in the morning, or as soon as they go up, and sit there all day long -- until the 5:30 p.m. show.
However, when the 5:30 p.m. CP is over, everyone who was viewing it has to shuffle along and move out so that the people waiting to view the 8 p.m. Ceremony can step into place.
If you want a bench for the 8 p.m. show, you would have to be up at the front of the waiting section -- and the Cast Members may or may not let people begin waiting for the 8 p.m. show while the 5:30 p.m. show is still happening. Last year, I began waiting for the 8 p.m. show at around 6:30 (while the first Ceremony was still happening), but there was already a substantial group of folks ahead of me in the waiting section on Main Street, who had presumably gotten there even before 6:30 -- and they probably scooted right over to the benches as soon as the Cast Members cleared out the 5:30 people and let us move ahead into Town Square.
If the benches are not important to you and you want to stand in a good spot -- as I mentioned, the Cast Members will probably let people move into Town Square for the 8 p.m. performance as soon as everyone from the 5:30 performance has moved out. Again, you'd have to stand in the designated waiting area on Main Street first (which could open up at 6:30 p.m. or even before that) -- this is sort of the waiting area for the waiting area, in a sense!
You're essentially waiting along Main Street -- to then move into Town Square and wait some more!!
I'm not entirely sure when the CMs will let people begin standing and waiting for the first performance at 5:30 p.m. Something tells me that they may vary it slightly, from year to year. Maybe some years they may let people move into the holding area on Main Street 90 minutes in advance. Maybe other years it might be 60 minutes, or 30. Maybe they just move people right into Town Square without standing on Main Street first. I'm not sure. Your best bet would be to ask the Cast Members in Town Square when and exactly where they will let people begin waiting that day.
This is also the first year of the CP when we have had the back alley behind Main Street officially opened up as a traffic flow corridor. That could impact the way the crowds move around, which could also affect when and where the Candlelight crowds are allowed to begin standing.
The narrator's podium is on the right side of the stage (when facing it). So if you move into the standing area on that side you will be closest to the narrator, but if you move too close to the front of that waiting area you may end up with more of a side/back view of the narrator. I was on the right side last year, and I almost wondered if I might have been able to get a better, more direct view of the narrator's podium from the front if I had stood on the left side instead. I would have been farther away on the left, but I think I would have had a more direct, clean eye line/view.
If you're not interested in waiting at all, you can certainly hear the narration and music from various points on Main Street or at the Hub. You won't get the full Candlelight experience that way -- the setting of Town Square in the haunting flicker of the candlelight is just lovely to see, and it's wonderful to watch the actual processional, as the performers file in and take their positions on and around the stage -- but you will be able to hear some really great Christmas music, sung by very talented people, and Beau Bridges' narration!
DO they sell gingerbread items too? Cause you know I'm obsessed with DLR gingerbread! LOL
I asked about the 5:30 performance on Saturday which is when I will be there. The CM said it would be advisable to ask that morning and weather may affect things. Otherwise, to arrive at Main Street by 3. There will be extra CM's and marked areas in which to wait. Other suggestion was to check periodically throughout the day to get a feel for crowds. 
