Back with Success!!!
Must say, boy that was a pain in the butt... I've opened up laptops before, but never an ultrabook... the parts are TINY!!! honestly it was a mistake to open it at home and I should've taken it to work to borrow a microscope or something. that aside, I took my time, was careful with handling the parts, and fortunately managed to not break anything. that side, Lenovo's mobo is actually discrete, and after disconnecting a dozen odd headers from various parts, it's actually possible to take just the motherboard out of the system (4" x 2" tiny thing). needless to say, this makes my work a bit easier.
The paste Lenovo happen to use is at least proper paste. that aside, whoever did it used a bit too much, so after a bit of cleaning I carefully applied a thin layer of arctic silver 5, re-tightened the heat-sink, then took it off to check the foot-print of my application. after adjusting again and applying what I think is the right amount, I put everything back together. then, taking inspiration from random forum posts I've seen, I decided to apply a layer of NON-CONDUCTIVE thermal compound, in this case arctic-silver ceramic, to the back of the die-area, allowing it to make contact with the aluminum-ish chassis. Lenovo did put a piece of plastic there to prevent any shorting, and I left that plastic alone. thus the laptop does not get scorching hot when I use it on my lap. and on the odd chance that I want to game from it or do anything intensive, I can set it down on a desk or hopefully a cooling pad.
As for my ultimate goal, I actually managed to lower the idle temp by 5 C, and load temp by nearly 10 C. while both are good, it's the idle-ish temp that was critical. apparently Lenovo had set the fan to kick on at 48 C, which used to happen randomly in a room of around 20-25 C. after my past reapplication etc, my idle or light usage temps sit around 40-46 C, so the fan almost never kick on while I'm typing up a word document or watching a movie 🙂
In the end, while it was well worth it in my case, it's not something I'd advise everyone to do. but if you're patient, careful, and have a nice pair of tweezers with decent grip, this could solve that burning laptop problem you've been having