To repaste, max RAM or install antenna into on Thinkpad P52 this post provides links and tips for full disassembly.
The disassembly is fairly easy as I was able to repaste and install LTE antenna without any previous experience, that is except removing LCD panel, which seems to be just glued onto the cover in a cheapskate manner. Concern is durability of screws on your machine as they can take only so much use before need for replacement. Some of my screws are at 60% mileage after 8-10 openings.
I recommend using the maintenance manual combined with a video linked in the corresponding sections below. You can find P52 vs ZBook G5 comparison on this site as well.
I personally did full disassembly due to having to clean up almond butter from all over the fans.
The non official download is much faster
I recommend using the amateur video below, but I am linking to official videos as well.
LCD Panel Removal - Not achieved
There is a video on Youtube on P51 LCD removal, but it does not apply to P52. P52 has screen glued with double-sided tape, due to which I was not able to remove the screen, forcing me to install LTE antenna in a hacky way.