Ok, my post count is high enough now.
The stock fans are press fit in. Simply use a small flathead screwdriver or hobby knife to carefully pry the stock fan out of the housing. Do one side at a time a time or two and the old fan pops out.
Once the stock fans are out, the housings need to be very lightly modified to use the new fans. This is because the stock fans routed the power leads differently than the Sunon fans. This is seen here.
