They only take a small tool box, a little logic on the wiring and about 3 hours to do it right! the prices range from $300 to $500 for a set depending on brand. There are very nice less expensive($300) sets avalable. I have a set like this with the vacuum actuators. Check out my pic below to see what the "euros" look like. they are quite different from US, internally and externally.
Hope this helps!
Adam

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320