I do 10 gallons every two weeks on my 55 gal reef tank by mixing up the SW in a couple of 5 gal buckets and letting it sit over night to aerate and warm up, then just siphon the old stuff out and pour the new back in by way of the sump. Definatly want to let it sit and mix for awhile so you can check the salinity and make any needed corrections before putting it in the tank. Proper salt/water mixing should result in good salinity/ph/alk levels when freshly mixed but you should always let the water mellow unless it is some type of an emergency and you have to large changes in a hurry.
I have heard 10% a week as a general guideline, but peoples practices vary widely. A couple of things to keep in mind: a large fish load may dictate more frequent changes, keep up on checking your nitrate levels with those fish. More frequent water changes will replace trace elements and will keep nitrates down, but you also have to consider the cost of salt, water, etc, etc, in figuring out just how often/how much to change water in your tank.
The water temp doesn't have to match the rest perfectly. As long as its close in range that works well. You can actually buy already salted water either at a store (where they often have it in 4.5 gallon cartons that are directly from the ocean) or premixed (which you can get at some salt places) the easiest way to do it is by mixing sea salt into distilled water. there really isn't a "proper" way to do it.