I took the spreader off my K6-2. It ain't easy. You've got to cut away at the epoxy on the corners but don't cut too deep towards the center of the chip or you'll gouge the surface mount resistors and possibly kill the chip. Here's a drawing of what a K6-2 / K6-3 looks like underneath.
Congrats on pulling the cap off successfully I have personally uncapped 2 K-6 class cpu's now, but personally noticed little to no additional cooling obtained from it. that cap is actually a pretty good tool for the actual heat dispursment. All you really need is a socket 370 fan and heatsink, and mabey some cooling cream (does not have to be arctic silver to make it work)... I personally use an Intel jobby rated for a ghz and have my (capped) K6-2 350 @ 450 mhz running stable withought any issues at all... I can get the chip to post at 500 mhz but does not boot yet havent bothered for more, got to get it up a bit by bit. Also take into conscideration these K6 series chips are running scarce now so be carefull, if you fry it, it is gone for good, and hard to find replacements. Not as if others do not have their opinion about buying a new setup which I am personally working on, but look at your budget... Can you afford to fry your setup and buy a new one? Take caution and dont push the limits of YOUR chip to the max if you cant afford to get a new one.