As far as PSU/mobo compatabilty, all that matters is what's called "Form Factor" (FF). The form factor of your PSU must match that of your mobo. For example, you must use an ATX FF PSU with an ATX FF mobo.
Older mobos have a 20-pin socket for the P1 connector; whereas newer mobos have 24-pin sockets for the P1 connector. Most PSUs have a 20+4 P1 connector that is designed to fit either style of mobo you have.
If you're concerned about the PSU being overkill, don't. Think of your PSU as a water reservoir. The power is "stored" in the PSU as water is stored in a reservoir. The PSU serves two functions:
1. Converts AC to DC
2. Sends power to the devices
So... if your complete build only requires/uses 450W (hypothetically) and you install a 1000W PSU, the extra 550W just isn't being used. With that said, there is no way a PSU will overload a mobo.