Want' aware asrock created a mb targeted to bitcoin mining lol.
Well it's only abundant with pci-e slots, get a good psu and you should be good also for litecoin mining with vga's, 4x7950 VGA are a common choice, but Vga mining for litecoin isn't anymore what it used to be thanks to the difficulty increase.
Ah, for interaction with your desktop while you mine you should keep a card free from mining (if you want to play game) or with low or dynamic intensity if you just wanna surf the web/office use.
If mining does harm your pc? Well if you don't have a good cooling yes, high temperatures are to be expected, but if you build it the right way it should work !
You mean vga's, 4x7950 or H61 Pro BTC are ok? or you mean use them simultaneously or better performance?