6 months enough time for first Ironman?

Welcome to BT.  There are a bunch of us doing Timberman and planning to get together up there.  Hopefully you can join us.

As to your question, you have enough time to follow a plan that should get you through an IM if you want but you'll have to commit soon.  Take a look at some of them and see if you have the current base, etc. to start any of those.  There are a few plans on this site (Beg. IM, Full IM, IM Bridge) as a start.  You have to join as a performance member to get the full detail, but you can read the summary and get an idea of the plan now.  And there are lots of others too.  Most of them should give you an idea of what kind of background/fitness level they assume before you start the plan.

That's probably a good idea.  Do some easy cycling and swimming early in the week (highly recommend the easy cycling the day after the race to help recovery) and then add in some easy running later in the week.  Then start the IM plan after that.

You could probabaly complete an IM but beware that since you do not have endurance training under your belt your body will be more susceptible to injuries during an IM build-up than another athlete than has done a marathon or two and/or a couple years of HIM races.

Also keep in mind that 17 hours is a LONG time to complete an IM and if you can get to T2 before the cutoff, you're pretty much home free if you can walk 4mph... 

Good luck and really be careful to avoid injury during your build up/peak period for the IM trng.