Customized assistance :D

[Boardmonkey]

Hello all, i've been using smf for a few years now with really no motivation, recently i got alot of motivation and im looking to do the following, i will try my best to be specific so you can help me to the best of your knowledge 

1st:

I have my html template set up for my index.html which im obviously going to transfer to PHP tonight, my first question is how do i tear apart the skin, heres an example of what i wanna do, below is a skin i randomly selected from the themes area;

http://custom.simplemachines.org/themes/index.php?lemma=2706

as you can see theres the header, say i dont like it, i much rather use my header for my overall site, how do i tear that out, it includes
"Home, help, search blah blah blah" my header consists of a bar running across the top part with my site name on it while having a nav-bar under it and thats all i practically want to do for the top part.

Do i take the forum and stick it into the header... do i stick the header in the forum... some help would be greatly appreaciated!

and part 2 of this question, i want to run the forum menu "home, search, messages ect. down the side of the forum, do they have a specific peice of code i need to find and how would i go about finding it..

i've added a "preview" of how i want it to look, just the lay out any tips or anything on how to make it would be greatly noted or anyone looking to be a kind person and giving me a hand would be great too xD

Also, how would i go about carrying the session through the site?