HELP: Alaskan can't do another Dark Dec-Feb! Want to bike Patagonia North!

[mrzz1]

Have a touring bike I've used f/CA-FL... do I need a mountain bike?  Is mid-Dec. a good time to start?  PanAm Hwy decent w/good camping possibilities? Tons of elevation? Thought winds went SE.  Will I get prevailing winds (a novelty on any trip)?  Not best big airport close to Patagonia to fly into... or what major city to fly out of if I only have 89 days of travel time.  What is reasonable.

REALLY APPRECIATE ANYONE OUT THERE THAT HAS SOME SOLID ADVISE!  I'm a retired teacher usually in good condition, though just had a knee replacement.  Should be up to the challenge by Dec. 2013.  Will trade help for fishing trip if someone is heading north.
Mr. Z