To remove the latch: pull the door panel off, undue the link rods attached to the latch after removing the window channel track that's in the way. It slides down and away from the door after you remove the single bolt holding it in place. Pull the rubber window channel seal out and leave it hanging from the opening at the top of the door skin[where ever is comfortable for you]
Remove the locking motor and its link rod.Take the latch screws out and don't forget the small allen screws at the top.

Lock Cylinder: Tricky first time out, remove the door panel and that window channel track along with the seal. Take the lock motor out too.
Undo the 8mm headed bolt at the inner side of the OUTER door handle pivot linkage, use a racheting 8mm wrench or a plain open ended one to get it out. It holds a single bracket in place, remove the bracket as well.
Use a screwdriver to slide the locking clip that's hidden at the trailing edge of the door inside the door [back edge]
The clip is a large horseshoe shaped clip that slides behind the alloy lock cylinder holder.
Once you have the clip out, then disconnect the electrical leads to the lock cylinder. This can be both a microswitch and the heated lock element that's visible around the lock cyl if your car is so equipped.
Take the clip holding the microswitch off of it and remove the microswitch as well. Leave the lock heater ring in place.

You should now be able to insert the key into the lock cyl from the outside and turn the lock cyl until it matches up with the mating slots in the outer door handle. Once you do this, it will be able to be pulled through the outer handle assembly and# into the inside# of the door.
It has to line up with the "cut-outs" in the outer door handle and be wiggled out with care, very tight fit.
You'll see how it fits into both the outer door handle and that alloy bracket once you get it out.

It will kind of tip out at the last section of the cylinder. I can't remember which way you turn the lock cyl to start the line up procedure, but the cyl will only come out one way, so it's either in the "unlock" position or the "lock" position.

Installing the lock cyl is harder, since you have to hold the lock cyl up to the outer door handle, line up the inner alloy bracket that the cyl passes through with the hole in the door and then insert and turn the cyl all at the same time.
THEN, without disturbing all this, you slide that bit clip into the CORRECT slot of the alloy bracket, while it's held tightly against the inner side of the door, and hope that you engage the alloy bracket and the right part of the lock cylinder all at the same time.

Check all of this with the parts out, so that it makes sense.
Once the clip is in correctly, you should be able to turn the lock syl with the key to both directions like you normally would.
Install the inner bracket of the outer door handle with that little 5mm bolt[8mm head] checking that you grease the pivot a bit and get the travel just right before tightening the bolt[it is adjustable]
Now install the microswitch and its retaining clip
Put the linkage rods back on.
Reinstall the locking motor.
Reconnect the electrical wires back up.
Try the lock again, this time with the door OPEN and the latch turned on the door to where it sit with the door closed[just rotate the catch]
Your key should work the lock cyl in all positions AND the microswitch must work in the deadbolt position and hold, then release when the key is moved to the unlock position.

This is a tough job the first time out, make notes on link rod location, or draw a picture.
Take heart, Sixes were much worse as you didn't have ANY room for access to that same clip that holds the lock cyl into the alloy bracket.
Neither the Seven or the Six is as easy as the E-28 Fives or the E-30 3s, but the Sevens and Six Series were designed earlier in the '70s, and their central locking parts show it.