Since you are only changing one (although your text wasn't entirely clear in this - do you know which one to replace or are you changing all of them?), my preference is to pull the rail with the injectors attached. This way there is less risk of crud falling into the exposed inlets and ruining otherwise good injectors. And if you remove them from the rail do it on your bench with the injector nozzle facing up, for the same reason.

Change the seals. All injector seals harden over time, and they're easy and (you don't always hear this here) they're cheap, too. It's better that a vacuum leak.

I wouldn't bother disconnecting the pump unless you want an arm/face and a garage floor full of gas. There is fair amount of fuel in the lines, and you would have to plug the line, or you'd just syphon all the gas out of your tank.

Disconnect the high pressure line at the injector rail (with a cloth handy). Disconnect the return line as well, and tilt the rail to drain it. Otherwise, when you fight with the injector and it comes flying off in a hurry when you finally win, you might end up flinging fuel all over the place. Cover the open lines until you are ready to reconnect them.

And keep that trouble light - hopefully with a compact flourescent - far away. They don't call it trouble for nuthin'.