I'm kind of curious as to the mechanics behind the Dwemer Ruins selection and had a few questions.

1. Is the ruin selection random or is it set?

2. I've only so far been able to recover the Shards that were at ruins I've previously located. So in able to get the rest of the shards, do I have to scout out EVERY ruin?

Thanks in advance.

Here is a walkthrough if its any help.

http://elderscrolls.wikia.com/wiki/Lost_to_the_Ages

In her journal there is a map. It also describes possible locations as well.

What does the walk through mean by "inside"? Inside on the Bridge? Is there a door hidden in the water? What? No ghost, no quest marker, no nothing.

This. Just compare her map to yours. They aren't hard to find.

The last one is bugged for me. I now have the location, but there's no shard and no ghost.

There isn't supposed to be a marker on the the last shard. It is not at Bthardamz, but at a location just north of it. If that one is not the one you are looking for, then go to Raldbthar (it is in the back of the ruin, just past the door to Blackreach), and then look in the Mzulft Gatehouse (just outside of the main ruin).

Many thanks to Ben5292001 for that tip on how to find the last shard at Bthardamz (or rather, just north of it beyond the Deep Folk Crossing). Was having a bit of trouble finding it without a compass bearing, and I hadn't kept track of the first three locations where the ghost gave assistance in the beginning; forgot which ones I'd been to already. Found the forge easy enough at the Ruins of Bthalft, though.

It clearly says in her notes "Not Bthardamz but North East of it"...

Yep. I actually enjoyed this quest more due to the (comparatively) hazy locations. A bit of a throwback to Morrowind's "It's in one of the caves in the hills over that way..."