how anyone can make money charging $100 to do that is beyond me.. it'll be a couple hrs minimum...
as you've learned from your throttle cable, things move when a bodylift is installed... you'll have to determine if any issues will arise from it moving back lower..
the areas that are usually modified, or are affected by a bodylift are...
fan to fan shroud... often times people either cut the bottom off a shroud, or mod it in some way so the fan can sit lower with the bodylift... check to make sure that the fan moving upwards 2" wont cause any clearance issues with a shroud, if it has one..
shift linkage... if it's a factory column shift auto, and not cable operated floor shifter, they may have extended or adjusted the linkage... make sure the trans operates correctly when done.. if it's a 4 spd, clutch Z-bar geometry should be checked...
gas fill and vent.... make sure the hose that attaches the metal fill tube under the truck that goes to the tank will not be kinked, pinched, etc once the body is dropped a bit...
steering column.... I'm not a first gen guy, so they'll have to come in and correct any misinfo here... but the column would be extended, telescoped out for the 3".. they will need to check that..
valve covers.... if it's a small block this shouldn't be an issue, but if someone has installed a BB or tall valve covers on the SB, you can have interference issues sometimes between the covers and the brake booster...
I would have a quick list so these things can be checked/mentioned to them... I would make sure they know that associated issues like these will need to be looked at too.. not just rip the pucks and mounts out and throw the new stuff in without checking these out..
also the brake lines from the master cylinder to proportioning valve should be looked at...
this is standard stuff for anyone who has done this a few times, but ya never know what clown could be working on your rig.. at $100, after fighting/cutting the old stuff out and installing new stuff, they would probably just give these items a cursory look, if that.. cuz they'll probably already have too much time in it..
I would make it a point to say if it costs $200 total to correct any these possible issues, your willing and you want it done right...
just go around the truck and look at it knowing the body is dropping 2" and what it will do to various areas.... I assume you've already taken tire clearance into account..
hopefully I'm not forgeting anything...