First off,
to the forum. There's a wealth of information available here. Just use the search feature located in the top blue bar located on every forum page. You'll find it's easy to use, but sometimes finding the right words to search for can be a challenge. Don't give up, just keep trying different terms until you find what you're looking for.
As for whether you need a sliding hitch or not, you'll find our membership is pretty much divided on that subject. Some will swear you absolutely must have one, some will swear just as much that you'd be wasting your money if you foolishly buy one. Most aren't that far from "center" with their thoughts, but whether you buy one or not is more a personal choice than a "must have" when towing a modern fifth wheel with the molded front cap.
There are some recent threads about the topic. Here are two in particular that will get you started in making your decision:
http://www.keystonerv.org/forums/showthread.php?t=15283
http://www.keystonerv.org/forums/sho...ight=clearance
Whatever you decide, the important things to remember are to be safe and to enjoy your travels.
Good Luck and again, welcome to the forum.