There is a new very decent fix to this problem. It involves simply installing a kext.
http://forums.macrumors.com/threads/gpu-kernel-panic-in-mid-2010-whats-the-best-fix.1890097/#post-23312990
Install it and be happy. A hardware fix involves replacing the capacitator - it is NOT the GPU itself that is defective. The problem is the capacitator, which costs just about 2$ -> 10-15$ including shipping.
But you need to remove the old one with soldering iron from the logic board and solder the new one onto it so it requires technical ability and also you need to remove the logic board before doing this, so the kext fix is easier. It only has the downside that the dedicated GPU does run only at 70% of its maximum capacity, and external displays can still trigger the kernel panic, as far as I have read. So if you need to use an external display the capacitator exchange would be better for you. Nevertheless test the kext first to confirm it is 100% the capacitator that is causing the kernel panics and then do the repair.