What would be a fair price to pay for a major tune up on an 04 Astro Van?

The GM stock units are NOT as good as aftermarket ones. Borg Warner makes a better distributor cap that seals better and has brass connector terminals in stead of aluminum. Keep the original wires unless they have oil rotted. Forget the Delco plulgs, they are made in mexico junk wads. Have your throttle body and IAC valve cleaned out. They control fuel mixture by adding and subtracting air. CLean everything out FIRST to showroom clean, THen add Bosch Fusion or Denso iridium plugs. They make the most of each piston stroke and improve power, economy, and give better MPG"S Also your converter and o2 sensor will last longer since less carbon is made. Price wise, not much if you do it yourself. $300 or less for a competent person. GOOD LUCK!! Your engine will FEEL turbo charged with the newer kind of plugs.

5 or 6 hundred bucks, dealer parts aren't cheap at all,but they are the best.