> Changing a camshaft in a classic car is huge pain that requires specialist equipment for setting the timing etc. and getting it wrong can destroy the engine.
That's overstating the case quite a bit. There are plenty of engines where you don't need special tools.
> I'm sure it's a lot more complicated on a modern car.
Wait. You were talking about older engines? Then, no. You're absolutely wrong. Swapping out cams on most older engines is a piece of cake. Pretty much anything without variable valve timing will be super duper easy. Pushrod motors are especially easy. There are some exceptions, of course, like the DeLorean's V6 (the cams slide out of the head so you generally won't have room to pull them out without pulling the head).
That's overstating the case quite a bit. There are plenty of engines where you don't need special tools.
> I'm sure it's a lot more complicated on a modern car.
Wait. You were talking about older engines? Then, no. You're absolutely wrong. Swapping out cams on most older engines is a piece of cake. Pretty much anything without variable valve timing will be super duper easy. Pushrod motors are especially easy. There are some exceptions, of course, like the DeLorean's V6 (the cams slide out of the head so you generally won't have room to pull them out without pulling the head).