Yes it is easy to fit and yes you will have to take the back off your computer. Here are some instructions for a TV capture card but the PCI firewire card will be very similar: http://ucsu.colorado.edu/~wilsonsl/iyonix/fitting.html
never take the back off your pc!!!!!
remove the side panel and the card in question can only fit i nthe correct slots so would be a piece of wee wee to fit
Whatever you do, make sure you take anti-static precautions. Electro-static discharge can kill the components of a PC stone dead, the human body can give off 6000 volts whilst only 30 volts will destroy a CPU. Preferably use a discharge strap or at the very least ground yourself by touching a radiator or similar before handling any electronic components.Also avoid touching the printed circuitry of the component, hold the card with the edges between your hands.