I don't see this going well. That machine is designed for a business with not much upgrading being done. Turning it into a gaming machine may end up costing close to what the machine cost you.
Looking at the pictures it looks like the CPU cooling is via a fan in the case and a "wind tunnel". It doesn't look like there is a real CPU cooler.
The board should fit in almost any mid tower case, but you're probably not going to have the metal plate for the mother board connections that go out the back, that normally comes with the mother board, and looking at the picture of the back you may need a Dremel or similar tool to cut holes in the back.
I don't know what your budget for this is, but you're almost looking at a new machine for the parts you'll need.