Here's an article that explains the process pretty well. In general, siphon the water out while vacuuming the gravel, then add in the new water (with water conditioner already in it and matched to the temp of the tank). You can also scrub down decorations with a toothbrush and rinse your filter media in either tank water that you pull out, or dechlorinated clean water, NEVER tap water. So, to answer your questions, yes, leave the fish in, and yes, match the temp of the tank. Also, for future reference if you do a simple google search on these types of questions before you ask them you can do some quick reading yourself. This will enable you to ask more specific questions about things you still don't understand, and then we know that you've done what research you can on your own and people are more inclined to help you.
http://www.cichlid-forum.com/articles/water_changes.php
It also helps if, when someone posts a suggestion for you, your response isn't "lol, you're wrong", which is basically what you said to my first response to one of your earlier posts. I'm just saying. You'll get a lot further by listening and then asking more questions, and responding to our questions than you will by ignoring/mocking us. Not trying to be mean, I just want you to get the best experience possible.