Have just completed the process of removing & installing new Monroe C1501S struts. Frankly, I would have gladly paid twice for the struts if the install engineering had been easier. Of all the PITA tasks, the most frustrating was removing the female connector from the male connector that is hidden and almost unreachable by an ordinary human being.
What I did realize, finally, is removing the spring & strut assembly allows a small amount of access to the connectors attached to the rear sub-frame from above the axle & disc brake. What was most helpful was an thin, 8" long slot blade screwdriver to pull the locking tab toward the center of the connector assembly. Once that is released, removing the strut connector is a comparative breeze. i think a 10" screwdriver would be an easier tool to reach into the nether world Volvo created for anchoring the connector receiver.
It helped somewhat to have a video camera with an internal light and 3' flexible scope to peer into the area where hands can barely squeeze.
An unappreciated issue is the force required to pull the suspension parts down. While VIDA instructions make the use of a ratchet & strap seem like an easy proposition; I found that anything less than 1.5" wide was just not able to create the pulling force required. I ended up with 1.5" strap and still found the use of a long 2x3 and a block to persuade the suspension down helped get more tension on the components.
It took me some experimentation to learn how to use the spring compression set I had purchased. At the conclusion of the process, I realized that a shorter and less complex spring compression tool is more useful in compressing the springs in the confined area of the chassis, to aid in the removal of the strut assembly, and in the installation of the strut Support Plate(s) (8646101).
The proper alignment of the spring seat (30748888) is crucial to getting the entire assembly correctly orientated for easy re-installation. I found the more marks and alignment points made for an easier reorientation of the spring, spring seat & strut assembly. My first attempt was just barely passable, but the use of multiple reference points made installing the second spring seat less of a challenge trying to position the spring properly in relation to the shock mount anchorage (8250447/48).
The flange bolt listed as item #2 (989035) in most parts manuals, at least for my vehicle, is incorrect. The bolt requires an integral washer. If I was to replace another set of struts, I would order a few extra Hood Lift Support Clip (9470602) for reattaching the new signal cables to the chassis.
When I got the old struts out, the bottom of the assembly was wet with strut fluid and dirt; the dampening action of the struts was next to nil and I understand why the car felt as if it would leave the road of it's own quixotic decision.
A labor and frustration reducing tool is a strut bolt socket. Kobalt makes a set with a ratchet that looks like it would make the strut nut removal, with a long T-40 Torx bit, much quicker with less frustration. I ended up using an 18mm impact socket that had a single hole drilled in the side along with a spanner wrench to remove & reinstall the strut retaining bolt.
If there is a next time, I think I might be able to get the process (not including the VIDA SUM re-calibration) completed in 6 hours.