t400 and some new upgrades Heat questions

[alsohere]

I purchased a T400 a few weeks ago, and I have finally purchased the requisite hardware for my upgrades.

I am installing a Momentus XT 750gb hd and 8gb of ram.

I would like to know how much of an improvement in heat control I would get if I apply MX-4 for the thermal compound, because the computer gets toasty now, and it will be worse with the higher load I will be putting on it?

I bought an OEM fan from IBM, because I am under the impression that like the t61 the t400 fans do not have the legs to make it much more than four years, if they get there.

I also wanted the second heatsink, because after the failure I install the crap fan from Amazon into the heat sink and wait for another death in the family.

The machine will be hook solely to the dock powering a 22in monitor --typist-- and the peripherals that are necessary.