yes raekwon....just did it to my SLK-900A today actually
You start with a somewhat coarse grit of sand paper depending on how bad the current heatsink base already is....then you steadily sand it on a piece of glass so its perfectly flat and to that for about 5-10 mins per grit of sandpaper and then move up to the next grit until you hit 2000..... at www.easypckits.com
he has a premium kit with the glass 10,000 grit polish and micron sandpapers. Real nice guy runs the site too. I've never lapped the actual CPU core and I don't think I'll be trying that....the idea just scares me.