Driveshaft installation

If you gently clean the output shaft on the transfer case and the input yoke on the differential there should be yellow paint dots. The new shaft should also have (usually yellow) paint dots. Line those up at both ends and that is it.
Be sure to use blue loctite on the bolts on the carrier and rear flange and tighten the flange bolts using a cross pattern so it seats fully and square.

If you bought the complete shaft it will go from the transfer case to the rear axle as the carrier bearing is part of the front section of the shaft as shown in the image. The two piece shaft has to be replaced as a unit to stay balanced.

Yes. It goes from the T-Case back to the carrier mount, then the rear section goes from the carrier area back to the rear differential flange. The whole thing is balanced as a unit.

With it not running you shouldn't lose any, the front yoke into the T-Case is above the fluid level and the rear yoke doesn't come off for the shaft to be replaced. Oh, If you noticed the image shows the wrong transmission, but the 4X4 works the same way. Depending on which case is in it you may have a front bolt on joint and not a slip yoke, Ford used both depending on which case design and which wheelbase and options you have.

In theory a new shaft should be balanced and ready to go. The marks are there just to eliminate any issues. Having the slip yoke version is a little easier, you don't need to hold the shaft in place to line things up, it just slides into the case. I would recommend changing out the seal in the case though, just to prevent any leaks. They can take a set from running on the yoke for a while and then don't seal as well on the replacement, they are a simple pry out and tap in design.

You're welcome.

Depends on how you are getting under it. On a lift I leave them in park because I can rotate a tire to move the driveshaft to line up bolt holes, if I'm doing it on ramps or on the ground I put it in neutral so I can rotate the output shaft to line them up.