1) To address your second post: Always boil your priming sugar in a small amount of water (2 cups or so) so it'll kill anything in it. You're probably fine though, so don't sweat it - just remember for next time.
2) to address your first questions, it looks like they've provided you with an amount of DME (5 oz) to use for a yeast starter, but the instructions actually say nothing about how to make the yeast starter (from what I can tell anyway - it's HUGE!). FYI you can read up about yeast starters at
http://www.mrmalty.com/ Yeast starters are only for liquid yeast. If you're brewing in 18 hours it's problematic for the yeast starter because you should allow a couple of days for the yeast to build up their numbers in the starter. Basically the way it works is you boil some DME (your 5 oz package of DME) in some water (1.5 quarts for the 5 oz DME) for 10-15 minutes, then cool it down to about 90F, put it in a sanitized container (such as a big mason jar or growler), then pitch the liquid yeast into that. Cover with a patch of aluminum foil. Let it sit at room temp & swirl often to get oxygen into it & keep the yeast in the solution. Let it ferment out for a couple of days. Then after you've brewed and have your wort down to pitching temperature (say 68F or so), you can decant off a bunch of the clear liquid (but not all), then swirl the yeast into solution and pitch that into your wort. In your case if you want to brew in 18 hours, you could probably just do all the steps above until you're ready to pitch the yeast starter, & just pitch it all into the carboy - it'll probably still be actively fermenting, which is fine (don't decant anything off in that case - a lot of yeast will still be in suspension).
3) If you have dry yeast instead of liquid, disregard the yeast starter. It'll actually weaken the dry yeast. In the case of dry yeast you should rehydrate it. Basically you boil a couple of cups of water for 10-15 minutes, let it cool to about 90F, then sprinkle the yeast on top. Let sit for 15 minutes then stir the yeast into the water (with a sanitized spoon of course - a good rule of thumb is if it will get boiled you don't need to sanitize it, but if it won't get boiled you do). The dry yeast is now ready for pitching.
4) What they mean by "remove crushed grains" just means dump them out of the bag they came in into the water (but hopefully you have a grain bag to put them in so they can be used like a "tea bag" in the water - if no grain bag you can just add them to the water and follow the instructions for the 152-158F steep for 30 minutes, then strain that water with a regular kitchen strainer into your boil pot - you might need to transfer them into a second vessel of some sort first, then into your brew pot which you were originally using for the grain steeping step). Hopefully your grains are already crushed. I assume they must be if they came with a kit. To check, all the grain kernels should be cracked and you should have some amount of pretty fine "dust" type stuff in the bag. If they're not, you need to have them crushed.
Hope that helps... definitely check into How to Brew by Palmer, like COLObrewer said ^^^.
Actually the instructions are pretty good. They just don't include what you should do with the 5 oz DME...