First question, the case only supports micro-ATX and mini-ITX motherboards
Second question, your license (through emachines/gateway/acer) is for the system with motherboard intact. A new license would be needed.
Third question, It uses a standard ATX PSU
Questions not asked (but should've been IMO)
Do I need new ram? Yes, your current ram is DDR2*, the motherboard you're looking at uses DDR3
Do I need a new CPU? Yes, your current CPU is socket 775*, the new motherboard uses socket 1155
Hope it helps
*Unless your model is newer than the one I could find to reference