Ok So You Should Have Two Blocks, Your Vocals And The Instrumental/Beat. RightClick On An Empty Block. Brings Up The Menu ... Then Click MixDown To Track, Then All Waves. Then Your Done Just Delete The Other Two Blocks/Tracks Vocals/Instrumental. Make Sure You Have Made All the Change To Ya Vocals Coz Ya Can't Do It While Its Mixdown- Fucks Up The Beat. Hope This Has Helped Ya.

Edit: The Quality... What I Do Is: Click On Effects-Noise Reduction-Hiss reduction-High Hiss Reduction. Then Click Ok. Also Click Effects-Noise reduction-Noise Reduction. Set The Noise Reduction Level To 95. Then Click ok. This Should Give You More Of A Pro. You Can Also Use The Filters ....