We are doing the Mongolia Charity Rally next year, leaving the UK on July 6th 2013. Maybe our paths will cross. Not decided what we are driving yet but possibly a Transit van as there will be three of us and that way we'll have three seats abreast.
Planning Europe, into Ukraine via Hungary or Slovakia, transit Russia into Kazakhstan, through Kaz and transit Russia via Barnaul into Mongolia, then either northern or southern route to Ulaan Bator.
Borders shouldn't be a problem, apart from the length of time it takes. No carnet required. Sort visas before you go, then when you arrive at the border get your passport stamped, and from customs, your vehicle entry stamped, buy insurance, exchange currency, and you're off.
Have a good trip.