I've been asked to photograph memorial services for two folks now. I've kind of pigeon-holed myself, because after the first one, I created a video using the still images that was very touching and with the last one (that was on Thursday) everyone is greatly anticipating the video.
I would agree for the most part with Frogroast with the exception of the long lens thing. If you've cleared your photography with the family, then there's no reason not to act like the photographer. With the first one, I had a nice vantage point in a balcony looking over the congregation, but with this one, I had to walk around the back perimeter of the church. The direction I was given from the church staff was not to cross the pew backs of the last row. I try to be very judicious about what I shoot, so there's not a lot of tears which might be embarrassing later.
The video is
here if you're wondering.