Spend the cash, get a reputable shop to do the upgrade, and have peice of mind that they will stand behind their work. You want to ask, and preferably have in writing their labor/workmanship warranty.
(I recently had to regear a ford explorer that was all stock, but was improperly spaced from the factory. There was a great deal of noise, and when disassembled i found that the gears had slowly been eating each other to the point making the gear teeth sharp as razors. That was an adjustment error of a few hundredths of an inch! )
$1000+/- is about right for a front & rear regear.
Parts alone will be $500+
I suggest that you do your own research, purchase your own parts, then have a shop install them for the $600+/-
I charge the going local rate of $375 per differential, and turn away any gearing job that I get the feeling will be abused. (racing & wheelin) It's a learned, intensive skill, includes not so cheap tools, and is a big responsibility. I'm replacing somthing that is designed to last the life of a vehicle, and a very small mestake can have expensive consequinces.
Don't cheap out on the bearing kits. The bearings are in my opinion more important than the brand of gears. High end Timken bearings are the way to go.
David @ northridge4x4 is very helpful & knowledgeable on the correct parts to use, nad has fair prices.