Overland from Beijing to Turkmenistan

Hi All,

I'm planning a trip for next year (June-July 08) in which I want to go overland from Beijing to Turkmenistan, probably passing through Kazakhstan and perhaps Uzbekistan. I read that there's a railroad that goes across northern China to Kazakhstan via Urumqi, but I haven't been able to figure out yet where it goes once it enters Kazakhstan, or if there are rail links onward from Kazakhstan to Turkmenistan. I also hear that the border crossing from China to Kazakhstan is a nightmare. Anyone been there or heard anything about the route? Much obliged for any & all information! Thanks!

Joe