There's a chance you've got the Project Video Properties set incorrectly for your video type. IE: You filmed in 720 but are trying to render in 1080.
When you're in Sony Vegas hold down Alt and hit Enter. This will bring up the settings. Under template, select different video settings until your video will play back normally in the preview. Once that's done and you're ready to render, hit file, render as, and then make sure the "Match project settings" box is ticked. I've found YouTube likes .wmv alright. ymmv.
You'll get used to your voice. Everyone hated their own voice the first time they heard it on a cassette tape. (aging myself)
Good luck.