ATX factor is a standard layout, just looking at the measurements of other boards will tell you.
only thing to bear in mind when moving parts is static, get yourself an anti-static band or ground yourself before removing parts.
and you can short equipment on the case without proper protection, but if you use the screws and mounts you're using currently it should be fine.
you can find out if you're motherboard is ATX by searching your computer online, if it was factory built it'll have a model number and if you look in device manager (right click my computer, properties its in one of the tabs) you may be able to find out there.
if you go to start > run and type DXDIAG, that tool will tell you what your board is. google the board