ok HII to everyone thank you for you time im sorta new to the whole truck thing.. Im use to working on classic porsche but  I've got a 1998  sierra 1500 2wd 5.0  that my older  brother gave to me ,its now my daily driver  its in almost perfect shape but id like to add some stuff here and there to get a little bit more out of it the first is to  upgrade the suspension shocks, spring, sway bars, bushings... suggestions?
and  id like to  to lower it so the front and rear are level and im having some questions Ive found a 6 inch difference from the rear to the front?? this seem like alot or is this normal?
also I would like to upgrade the brakes any sugestions ?? something thats got
alot of stoping power and wont cost an arm and  a leg..?
and  for the motor and trans are these reprogramers worth it? and superchargers   I would like to put oneon the truck but ive heard that they can only be put in brand new engines do to  stress level its use to? is this true?  

thanks for you time and help!!  

the difference between the front and rear end height is because the front springs of your truck are probably wore out. How many miles are on the truck?

DJM, Bell Tech, McGaugheys and Chassis Tech all make some good kits to drop your GMC.

EBC Brakes makes great aftermarket pads that stop better than stockers and wont cost an arm and a leg.

Programmers work well when combined with a good cold air intake and exhaust system. Hypertech makes a nice piece for  your GMC.  I wouldn't worry about stress on the engine from a simple computer programmer. But if your transmission is already slipping you wont want a programmer to firm up the shift points because the increased line pressure will only make things worse.

hope this helps.