I've now needed to replace two logic boards from liquid metal TIM damage!
While the heatsink plate is nickel with a copper heat tube the risk is the fact this stuff travels! Unlike normal TIM overtime the liquid metal will creep out and find its way to the CPU/GPU base board shorting things out. The space is so tight in a laptop I just don't recommend it. The amount of improvement is not enough given the risks.
Also keep in mind this is a Core 2 Duo based system so it's just not able to run heavy apps or games we have today. At the time this baby was introduced running a video off of the optical drive was pushing it!
I would recommend you stick with ArcticSilver 5 TIM and make sure you full clean the clips & heatsink before applying it. Don't forget to dust out the system, fan & heatsink fins as that will have more of an impact.
And lastly, look at maxing out the RAM and maybe even upgrading to a SSD if you really want to gain performance and lower the heat.