I've done quite a few of these. You should have to people for this job. I have done one by myself, but there is too much risk of breaking the headliner in the sunroof area.

Start by removing the visors, side trim, dome light, the clip above the dome light, sunroof mechanism trim, and anything else in the way.

The headliner goes out the right front door, diagonally. The left side of the headliner goes against the lower front corner of the door frame, and the right side goes against the upper rear corner of the door frame. You'll want to have the front passenger seat to the rear, and fully reclined. The driver's seat will have to be reclined a little. The headliner will have to be bowed a little. I sometimes take the door gasket off for a little more clearance, and you can also remove the right console side, but that is not necessary.

To replace the sunroof headliner, you'll have to remove the sunroof and pull the mechanism out the top.

Respond to this post with your email address, and I'll send you a file on replacing the headliner.

I've done replaced headliners in five 700/900 sedans, and one wagon.
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john