Converting a two wheel drive truck into a four wheel drive truck is a truly difficult job and given your trucks relatively modern model year it would not only include the mechanical components but electronics as well. You would have to set up all of the transfer case linkages both mechanical and vacuum, put in all of the electrics associated with the four wheel drive system, and of course you would have to set up the front drive axle which may not be easy due to differences between two wheel and four wheel drive truck frames (some of the mounting points may be in different locations or nonexistent ).
In closing I would suggest purchasing a four wheel drive model to begin with. It will ultimately save you a lot of time, money, and many, many hassles.
