They've got a great program and take good care of you out in the field. As for the cost, they've got current pricing on the site if you dig around. Figure about $3K for the 4-day and near $5K for the week trip.

A friend won a package from them at the SEMA show and invited me along to split driving/co-driving since I had co-drove for him in the 1995 La Carrera Pan Americana in mainland Mexico. Generally though you want to split it with someone you know since it's a driver/co-driver format.