Don't know about difficulty, but it is a little time consuming due to all the extra stuff that needs to be removed/reinstalled. It all depends on skill level and experience in wrenchin'. From what I'v heard, experienced techs who have done a few usually have no problem doing them in less than a day.
What year is your truck? If it's an '01-'02, your covered to 200,000 miles.
On Edit: I just looked at your other posts and see you have an '01 so you should't have to worry about DIY injectors for a while.
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