The tissues are a callback to the movie, and also a signal not to shoot them.
The scene where Shar'e is implanted with a goauld was forced on the production by SHOWTIME. They wanted to sex the show up, and THAT was the direction they decided to go with it.
The snake like goauld are similar to buffyverse vampires. Once you have one stuck in you, you're out of the drivers seat, and the snake is in.
Next time you see her, pause the show and look at her hat, it's a funny joke from the costume designer.
On the DVD special features, Don S. Davis talks about getting his showbiz start as a body double on MacGyver.
His last role was a reprisal of General Hammond for a stargate movie.
He tends to be on the ball in most episodes, and frequently calls on the main team's BS. I think I already mentioned he REALLY HATES the Quantum Mirror.
The MP5 SMG actually did have that flaw where the 9 mm round failed to penetrate vehicles, so there is some ricochet, but the Jaffa do tend to die if the soldier concentrates enough fire on them.
The planet from the original film, Abydos is used by the Goauld for two purposes - breeding attractive hosts, and mining space metals for their spaceships and staff weapons.
I found a picture of the power cell
http://www.stargate-sg1-solutions.com/wiki/File:216_liquid_naquadah_staff.jpg