My c860 also came from K. The price was good, and he shipped within 24 hours of my placing the order. I had some trouble with the USPS (they lost the package for a few days, and then found it again), but that's not K's fault.
I also did not pay any customs fees or duty on it. But K underinsured it (for $200). When the USPS misplaced it, I was left wondering who would bear the cost if it completely disappeared. Never got an answer from K about that.
If you are going to buy from him (and I see no major reason not to), I suggest insisting on full value insurance, even if it leads to some customs fees.
Second the recommendation for the Cacko ROM, too. I've tried pdaXrom and Opie. Both look promising, but neither is quite ready for prime time yet. Cacko is 100% English, and seems to be stable.
theKompany provides tkcROM for the 5xxx series, but there is no c760/c860 version. According to the person I spoke to there, the ROM is apparently now abandonware. They have not been able to contact the author for a few months, and don't seem interesting in providing any further support, not even to the point of finding the sources and making them available.