Take a look in the magazines for the prices and do it yourself if you can; installation will probably be a day charged at whatever the local shop rate is.
Cheap lift w/ shocks is gonna be about $300USD or so with blocks, and $500USD or so with rear springs.
Say 60 bucks an hour shop rate, 8 hours, $300 lift, taxes, *unforeseen* problems; I'd imagine youd be lucky to come out with the whole deal coming in under a grand.
Read around, there are cheaper and better ways to lift your truck than buying full meal-deal kits, and if you install them yourself you'll have cash for the other mods you are going to want to make.
Installing a lift on your truck is no where as difficult as you might think. I got no idea how much work you've done on trucks in the past, but lifting a solid axle rig like yours is a straight forward process.
What do you plan on doing with this blazer? Do you intend on playing with it at all?? Daily driver??
Whatever you do I strongly recommend reading the posts here and at www.coloradok5.com
before you make any decisions about what lift to buy.
Happy travels with the new GM!