I just followed the advice from here (Uneven CPU thermals! - #153 by taezea) to hit the CPU hard, then turn off and flip over. I let everything cool for at least 5 minutes before starting disassembly, and I was probably 30 minutes in before getting to the heatsink removal step. I would recommend just following the official instructions since it wasn’t that difficult. Work around the edges slowly, using the provided spudger, and the heatsink should break free. I didn’t have any board or heatpipe flex as rotated the spudger to lever it upward, and I didn’t pull on the heatpipes.
The LM actually cleaned off really easily. Most of it broke free as a large piece, and the smaller pieces easily adhered to my isopropanol-soaked paper towels