In thinking about the comment's left by self installed header owners, I've seen comments ranging from 6-8 hours to 12-18 hours. Several of those installs were very frustrating, I mean the I'll never do this again kind or what was I thinking when I started. Frankly, IMO I would see how much you can get them installed for, knowing the price ranges paid (sometimes too much sometimes suspeciously low) I would say the average is $300-$400. Only you can decide what YOUR willing to pay if at all.
Here, take a look at this how to with pics. This will give you a idea of what you'll be doing or what a shop will be doing.
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