If the fan is turning, the lights are on, etc, the PS is probably ok. Lightning isn't the only thing that can fry a board. My guess is that it's fried.
Now to your question: If you have a relatively modern system, not at all. It's all modular.
The issue is what you have that goes with your board. Every time I blow one of the suckers (not that often) I find that the memory, video card, ATA drive, yadayada I was using is no longer compatible with current standards and somehow end up slapping down about $500 for a slew of new products from video cards to memory, but end up happy.
In addition, if you have a proprietary system like an ACER or HP, there is a fair probability that your connectors won't fit into the slots in the new board. (How would I know this, you may well ask..?) Sitting in front of your benighted ACER case and trying to figure out if there is a way to separate out the solid state connector bank to fit in the standard configuration of an ASUS board is pretty annoying.
Most new boards, in addition, only come with one ATA slot, which will hold one optical drive and one hard drive. If your computer is over a couple of years old, you may have a couple of ATA drives, so you either need to get a SATA connector (no big deal) or a new second drive.
What I eventually figure out is that a blown board is a fair excuse to update to the next level of equipment, which will hold longer for you, rather than trying to patch an older machine.
If you do decide to upgrade you had best take it to a local computer place, buy there and have them replace the chip, since bending a pin makes everything more expensive and infuriating (how would I know this, you may well ask..welll..oh, never mind.)
Also: Be sure to ground yourself, best with a wrist strap if this is the first time. (Putting your bare foot against the radiator works, but is a little undignified).
So what brand do you have and how old is it?