How would you do this??

Hey -- complete newbie here, my seeds came in from attitude (5 ww fem, dinafem grapefruit, roadrunner, Cali hash and 2 other freebies). That is a good start- to let everyone know I have watched alot of Jorge Cervantes, high times video and the green dude from b.c. Also have Cervantes book on my iPod (indoor outdoor medical bible). I believe that I have hit maximum meltdown with all of the information that I have read and saw for the past month!!!
I'm in Michigan, have my mm card,will be getting a couple more clones to make my 12 plant limit, the only place I have to grow is a shed that is 6x12 wood framed with a floor and shingled roof, insulate it and heat it I should be good to go!!
Questions now-- My plan is to place baseboard heat for the winter in it,wrap the walls, floor and ceiling in Mylar. 400 watt metal halide for veg and a 600 watt hps for flower, plan on using soil- (not quite sure of any type of hydro and limited funds)-- don't know if I need to double the lighting for the 12?
6" inline through the lights to exhaust- or use that heat to supplement the winter cold?

Humidity too low or high?? Anyone done this same setup b4??

With the cold should I even introduce it into the rooms??
Any type of input would rock!! I know outside in the winter months will be a challenge and would obviously like to make it work.

Suggestions-- thanks

Mylar,

What I mean by introducing cold air -- is the fresh air from outside-- would it b needed??