Don't try to remove the CPU heat sink - it shouldn't be in the way. There are four of the plastic standoffs, all you MAY have to do is pinch the "split" top together to make it easier to pull the board off. Be careful not to wiggle the board too far from side to side or you'll damage the connector at the right hand side and make it intermittent.
A small flat blade screwdriver is the best tool to get the ROMs out (if you haven't a proper chip remover).
tony
