I just did one. I needed a tube for a K7500, and I've seen them in Zenith, Philips and Samsung varieties. I just so happened to find a Samsung dumped at the end of the drive outside one of my neighbors houses, and it was made the same year (1998). since I was taking a TV and making it medium res, I had to swap the yoke over from the old Zenith tube.
I did a dry run with it and it worked, then I swapped it to the frame. I replaced the degauss coil and ground strap from the old tube to the new as well.
it's really not all that complicated. the worst part was getting the convergence rings off heh
try to stick to the same make though. whatever your tube is now, seek out that brand, and if you're lucky like me, you'll find it from the same year or something.