A humbucker will NOT hurt any of your gear. Or, more accurately, any manufacturer who made a piece of gear which would not work with half the guitars on the market (roughly) would be extremely stupid. Since none of these guys are, it won't.
Don't worry about it.
As for pots, 250k is typical for single coils, 500k for humbuckers. This does NOT mean that this is a requirement. Either value will work just fine for any passive pickup. Some Teles even use 1Meg pots. Higher values tend to be brighter, lower values warmer (hence the common values, a brighter pot to help with the mushiness of a humbucker, and a warmer pot to help with the shrillness of a single coil).
Higher resistance means a higher output pickup, but lower resistance gives you a more even frequency response. Different gauges of pickup coil wire give you different resonant peaks in your pickup, meaning that the peaks and dips common to high output pickups will be different, even for the same output impedance (which can be determined by multiplying DC resistance by 1.25, which is why we measure DC resistance, which aside from its relationship to impedance is meaningless). If you look at low impedance pickups, such as Bartolinis, they use very few windings on their pickups, which leads to the very even frequency response. They don't drive a tube amp right though, if you ask me. But if you want a high fidelity sound (and if you play rock, you DON"T) you go with a low impedance pickup.
Light
"Cowards can never be moral."
M.K. Gandhi
