It's simple, ford dealers go by the book regardless of how much time it truly takes. I would think they are competent enough to get it right, but a grand is alot.
While i'm cool with guys doing it as side jobs, you can't really quote those prices, they have no overhead, insurance and nobody else is getting a cut of that money. So $150 gear changes are going to be few and far between, they are also risky considering if the installer botches the job there is no accountability.
Fair going rate on labor alone is between $250 and $500.
As for doing it at home, i agree with whoever said earlier it may not be a noob project. Rears are about the details and if you aren't detail orientated, it may not be the place to start. Seasoned professionals screw rears up, imagine what someone with no experience at all can do.
Not saying it can't be done, just realize, it's risk vs reward, if it works out you're golden, if you mess up, your rear may eat $1000 in parts.
IMO, find a professional people trust that has fair pricing and just let them do it.