You really need to have footings and a good overall design before starting. Talk to an Architect or if too expensive a good designer in you area. From the description of work it sounds like an awful lot of work for a DIY project.
IN n'ville or just outside ? 1st ck w/bldg permit/const office to see what you need,,, i'm in ga & some parts down here don't care while others ***** & moan if you lop off a tree limb ( guess where my bride, nagzilla, wants to live ) w/o a permit,,, you won't be adding a lot of static weight.