1
Some good info here:http://www.thepinaysolobackpacker.com/2011/06/25/overland-travel-kota-kinabalu-to-brunei/
2
I can go overland from Kota Kinabalu to Burnei?Yes, you can. You can find some details in the link provided by surfboy in #1. You can look for other routes in the web of Wikitravel (but you would need to verify schedules on the ground).
BTW, this is the web of the (a?) bus company that has direct buses from Kota Kinabalu to Bandar Seri Begawan (and v.v.).
