The manual outlines the deck leveling/adjustment but I wouldn't really recommend that you try it. It can be a frustrating process if youre not accustomed to doing it. You may want you have your dealer adjust the deck for you. It's a whole lot easier if you've done it a few times.
Chances are you'll only get part of the cutting height back. There's only about 1/2" of adjustment in your machine. If youre off more than 1/2" you'll probably need to look at some items that may be worn or damaged. First I'd look at the "arm wldmt 103-1500-03", deck lift as well as the "arm deck lift 1-633068" and clevis pins. These are all in the front frame section of your parts manual. I would recommend that you verify the part numbers in your manual. Without your serial number I sorta guessing when your machine was actually built. Again you may want to have your dealer inspect these parts in the deck lift mechanism. If they are showing signs of wear they should be replaced.