2004 shock replacement

Bought my first Toyota truck a few months ago. Its a 04 dbl cab trd 4x4 with about 53,000 miles on it now but the stock shocks suck. I can feel every bump in the road plus the truck feels like it floats or sways alittle (maybe the tires?) down the road. I don't have much $$ but was thinking about replacing the shocks with some 5100's.

I've tried reading up on all this here but my question is are the front coils ok to use with the 5100's set at the 0 setting or should I spend the little extra cash for some new coils? I thought I read somewhere that the stock coils are a little soft to use or something?

Down the road I would like to eventually do a small lift and level things out. I currently have some 255/70/16 tires and would like to replace them with some 265/75/16 when they wear out. The rear passanger side has a little lean of about 1/2" but the leafs will have to wait. When I do lift will I need the differential drop kit or is that only for when you lift so many inches?