I would check your flights if I were you. French air traffic are on strike for the next 6 days and loads of flights are being cancelled.
Transfers, as above, or I’ve used these before, at least for ski transfers – http://www.a-t-s.net/
Might be some local bus transfers also.
Guiding – You realise it’s Passportes du Soleil weekend? If not, you can just attach yourself to the route and follow it. Easy enough to find a map, but it’s waymarked anyway. I would assume the route remains waymarked for the season, though not sure. If you wanted to do it that is. If you want other stuff, can’t help, though there are plenty of guides I’d assume. Is as said short notice though. Still, a lot is on maps and waymarked. Chatel itself is one big bike park.
p.s. if you wanted an entry for Passportes, we have one spare, though starting in Morzine – http://singletrackworld.com/forum/topic/anyone-need-an-entry-for-the-passportes 😉