Starting point...
Do a COMPLETE inspection of the truck.
Mechanical
Electrical
Body
Cosmetic (trim, chrome, interior panels)
Make notes of what is good and bad.
Make a list of options you want to add or change (gears, p/s, p/b, trans update)
Be as complete and specific here as you can be. (Try to envision your finished project, make ALL your changes as you are putting the truck back together.)
If you don't already have a digital camera or a Polaroid, buy one before you begin.
Collect an assortment of baggies, boxes and containers you can label.
As you start dismantling, take pictures of the area you are working on, put all fasteners, bolts etc into boxes/ baggies and label them immediately, this WILL save you time and frustration when all is going back together.
As for the order in which you should do the work....
Start at the top , then the interior, then move to the front of the truck and dismantle the body. Brace the body tub across the doors before removing the tub from the frame.
All the mechanical should be handled the same way... front to back or back to front doesn't really matter, as long as you stay organized.
Be prepared for extra costs along the way.... a job done right the first time is much more satisfying than one that you have to go back in and replace or repair something you scrimped on!!
Let us see your progress ( post some pics) and remember to have fun!!
